diff --git a/externs/closure-types.js b/externs/closure-types.js
index 5f243df172..dd404bce5b 100644
--- a/externs/closure-types.js
+++ b/externs/closure-types.js
@@ -19,29 +19,33 @@ function Polymer_PropertiesChanged(){}
 * @param {string} property Name of the property
 * @param {boolean=} readOnly When true, no setter is created; the
   protected `_setProperty` function must be used to set the property
+* @return {void}
 */
 Polymer_PropertiesChanged.prototype._createPropertyAccessor = function(property, readOnly){};
 /**
 * @param {string} property Name of the property
 * @param {boolean=} readOnly When true, no setter is created
+* @return {void}
 */
 Polymer_PropertiesChanged.prototype._definePropertyAccessor = function(property, readOnly){};
 /**
-* @return {undefined}
+* @return {void}
 */
 Polymer_PropertiesChanged.prototype.ready = function(){};
 /**
-* @return {undefined}
+* @return {void}
 */
 Polymer_PropertiesChanged.prototype._initializeProperties = function(){};
 /**
 * @param {Object} props Bag of property values that were overwritten
   when creating property accessors.
+* @return {void}
 */
 Polymer_PropertiesChanged.prototype._initializeInstanceProperties = function(props){};
 /**
 * @param {string} property Name of the property
 * @param {*} value Value to set
+* @return {void}
 */
 Polymer_PropertiesChanged.prototype._setProperty = function(property, value){};
 /**
@@ -57,15 +61,15 @@ Polymer_PropertiesChanged.prototype._getProperty = function(property){};
 */
 Polymer_PropertiesChanged.prototype._setPendingProperty = function(property, value, ext){};
 /**
-* @return {undefined}
+* @return {void}
 */
 Polymer_PropertiesChanged.prototype._invalidateProperties = function(){};
 /**
-* @return {undefined}
+* @return {void}
 */
 Polymer_PropertiesChanged.prototype._enableProperties = function(){};
 /**
-* @return {undefined}
+* @return {void}
 */
 Polymer_PropertiesChanged.prototype._flushProperties = function(){};
 /**
@@ -74,6 +78,7 @@ Polymer_PropertiesChanged.prototype._flushProperties = function(){};
   call to `_propertiesChanged`
 * @param {!Object} oldProps Bag of previous values for each property
   in `changedProps`
+* @return {void}
 */
 Polymer_PropertiesChanged.prototype._propertiesChanged = function(currentProps, changedProps, oldProps){};
 /**
@@ -87,6 +92,7 @@ Polymer_PropertiesChanged.prototype._shouldPropertyChange = function(property, v
 * @param {string} name Name of attribute that changed
 * @param {?string} old Old attribute value
 * @param {?string} value New attribute value
+* @return {void}
 */
 Polymer_PropertiesChanged.prototype.attributeChangedCallback = function(name, old, value){};
 /**
@@ -94,23 +100,26 @@ Polymer_PropertiesChanged.prototype.attributeChangedCallback = function(name, ol
 * @param {?string} value of the attribute.
 * @param {*=} type type to deserialize to, defaults to the value
 returned from `typeForProperty`
+* @return {void}
 */
 Polymer_PropertiesChanged.prototype._attributeToProperty = function(attribute, value, type){};
 /**
 * @param {string} property Property name to reflect.
 * @param {string=} attribute Attribute name to reflect to.
 * @param {*=} value Property value to refect.
+* @return {void}
 */
 Polymer_PropertiesChanged.prototype._propertyToAttribute = function(property, attribute, value){};
 /**
 * @param {Element} node Element to set attribute to.
 * @param {*} value Value to serialize.
 * @param {string} attribute Attribute name to serialize to.
+* @return {void}
 */
 Polymer_PropertiesChanged.prototype._valueToNodeAttribute = function(node, value, attribute){};
 /**
 * @param {*} value Property value to serialize.
-* @return {(string|undefined)}
+* @return {(string | undefined)}
 */
 Polymer_PropertiesChanged.prototype._serializeValue = function(value){};
 /**
@@ -156,7 +165,7 @@ Polymer_PropertyAccessors.prototype._definePropertyAccessor = function(property,
 Polymer_PropertyAccessors.prototype._initializeProperties = function(){};
 /**
 * @param {*} value Property value to serialize.
-* @return {(string|undefined)}
+* @return {(string | undefined)}
 */
 Polymer_PropertyAccessors.prototype._serializeValue = function(value){};
 /**
@@ -206,7 +215,7 @@ function Polymer_TemplateStamp(){}
 */
 Polymer_TemplateStamp.prototype._stampTemplate = function(template){};
 /**
-* @param {Node} node Node to add listener on
+* @param {!Node} node Node to add listener on
 * @param {string} eventName Name of event
 * @param {string} methodName Name of method
 * @param {*=} context Context the method will be called on (defaults
@@ -215,7 +224,7 @@ Polymer_TemplateStamp.prototype._stampTemplate = function(template){};
 */
 Polymer_TemplateStamp.prototype._addMethodEventListenerToNode = function(node, eventName, methodName, context){};
 /**
-* @param {Node} node Node to add event listener to
+* @param {!Node} node Node to add event listener to
 * @param {string} eventName Name of event
 * @param {Function} handler Listener function to add
 * @return {void}
@@ -355,19 +364,24 @@ Polymer_PropertyEffects.prototype.__templateInfo;
 Polymer_PropertyEffects.prototype._stampTemplate = function(template){};
 /**
 * @override
+* @return {void}
 */
 Polymer_PropertyEffects.prototype.ready = function(){};
 /**
-* @return {undefined}
+* @return {void}
 */
 Polymer_PropertyEffects.prototype._initializeProperties = function(){};
 /**
 * @override
 * @param {Object} props Properties to initialize on the instance
+* @return {void}
 */
 Polymer_PropertyEffects.prototype._initializeInstanceProperties = function(props){};
 /**
 * @override
+* @param {string} property Name of the property
+* @param {*} value Value to set
+* @return {void}
 */
 Polymer_PropertyEffects.prototype._setProperty = function(property, value){};
 /**
@@ -381,19 +395,26 @@ Polymer_PropertyEffects.prototype._setProperty = function(property, value){};
 Polymer_PropertyEffects.prototype._setPendingProperty = function(property, value, shouldNotify){};
 /**
 * @override
+* @return {void}
 */
 Polymer_PropertyEffects.prototype._invalidateProperties = function(){};
 /**
-* @return {undefined}
+* @return {void}
 */
 Polymer_PropertyEffects.prototype._flushProperties = function(){};
 /**
-* @override
+* @param {!Object} currentProps Bag of all current accessor values
+* @param {!Object} changedProps Bag of properties changed since the last
+  call to `_propertiesChanged`
+* @param {!Object} oldProps Bag of previous values for each property
+  in `changedProps`
+* @return {void}
 */
 Polymer_PropertyEffects.prototype._propertiesChanged = function(currentProps, changedProps, oldProps){};
 /**
 * @override
 * @param {Object} props Properties to initialize on the prototype
+* @return {void}
 */
 Polymer_PropertyEffects.prototype._initializeProtoProperties = function(props){};
 /**
@@ -437,7 +458,7 @@ Polymer_PropertyEffects.prototype._hasReflectEffect = function(property){};
 */
 Polymer_PropertyEffects.prototype._hasComputedEffect = function(property){};
 /**
-* @param {(string|!Array.<(number|string)>)} path Path to set
+* @param {(string | !Array.<(number | string)>)} path Path to set
 * @param {*} value Value to set
 * @param {boolean=} shouldNotify Set to true if this change should
  cause a property notification event dispatch
@@ -486,13 +507,13 @@ Polymer_PropertyEffects.prototype.setProperties = function(props, setReadOnly){}
 */
 Polymer_PropertyEffects.prototype._propagatePropertyChanges = function(changedProps, oldProps, hasPaths){};
 /**
-* @param {(string|!Array.<(string|number)>)} to Target path to link.
-* @param {(string|!Array.<(string|number)>)} from Source path to link.
+* @param {(string | !Array.<(string | number)>)} to Target path to link.
+* @param {(string | !Array.<(string | number)>)} from Source path to link.
 * @return {void}
 */
 Polymer_PropertyEffects.prototype.linkPaths = function(to, from){};
 /**
-* @param {(string|!Array.<(string|number)>)} path Target path to unlink.
+* @param {(string | !Array.<(string | number)>)} path Target path to unlink.
 * @return {void}
 */
 Polymer_PropertyEffects.prototype.unlinkPaths = function(path){};
@@ -514,7 +535,7 @@ Polymer_PropertyEffects.prototype.unlinkPaths = function(path){};
 */
 Polymer_PropertyEffects.prototype.notifySplices = function(path, splices){};
 /**
-* @param {(string|!Array.<(string|number)>)} path Path to the value
+* @param {(string | !Array.<(string | number)>)} path Path to the value
   to read.  The path may be specified as a string (e.g. `foo.bar.baz`)
   or an array of path parts (e.g. `['foo.bar', 'baz']`).  Note that
   bracketed expressions are not supported; string-based path parts
@@ -526,7 +547,7 @@ Polymer_PropertyEffects.prototype.notifySplices = function(path, splices){};
 */
 Polymer_PropertyEffects.prototype.get = function(path, root){};
 /**
-* @param {(string|!Array.<(string|number)>)} path Path to the value
+* @param {(string | !Array.<(string | number)>)} path Path to the value
   to write.  The path may be specified as a string (e.g. `'foo.bar.baz'`)
   or an array of path parts (e.g. `['foo.bar', 'baz']`).  Note that
   bracketed expressions are not supported; string-based path parts
@@ -540,32 +561,32 @@ Polymer_PropertyEffects.prototype.get = function(path, root){};
 */
 Polymer_PropertyEffects.prototype.set = function(path, value, root){};
 /**
-* @param {(string|!Array.<(string|number)>)} path Path to array.
-* @param {...*} items 
+* @param {(string | !Array.<(string | number)>)} path Path to array.
+* @param {...*} items Items to push onto array
 * @return {number}
 */
 Polymer_PropertyEffects.prototype.push = function(path, items){};
 /**
-* @param {(string|!Array.<(string|number)>)} path Path to array.
+* @param {(string | !Array.<(string | number)>)} path Path to array.
 * @return {*}
 */
 Polymer_PropertyEffects.prototype.pop = function(path){};
 /**
-* @param {(string|!Array.<(string|number)>)} path Path to array.
+* @param {(string | !Array.<(string | number)>)} path Path to array.
 * @param {number} start Index from which to start removing/inserting.
 * @param {number} deleteCount Number of items to remove.
-* @param {...*} items 
+* @param {...*} items Items to insert into array.
 * @return {Array}
 */
 Polymer_PropertyEffects.prototype.splice = function(path, start, deleteCount, items){};
 /**
-* @param {(string|!Array.<(string|number)>)} path Path to array.
+* @param {(string | !Array.<(string | number)>)} path Path to array.
 * @return {*}
 */
 Polymer_PropertyEffects.prototype.shift = function(path){};
 /**
-* @param {(string|!Array.<(string|number)>)} path Path to array.
-* @param {...*} items 
+* @param {(string | !Array.<(string | number)>)} path Path to array.
+* @param {...*} items Items to insert info array
 * @return {number}
 */
 Polymer_PropertyEffects.prototype.unshift = function(path, items){};
@@ -584,7 +605,7 @@ Polymer_PropertyEffects.prototype.notifyPath = function(path, value){};
 Polymer_PropertyEffects.prototype._createReadOnlyProperty = function(property, protectedSetter){};
 /**
 * @param {string} property Property name
-* @param {(string|function (*, *))} method Function or name of observer method to call
+* @param {(string | function (*, *))} method Function or name of observer method to call
 * @param {boolean=} dynamicFn Whether the method name should be included as
   a dependency to the effect.
 * @return {void}
@@ -592,7 +613,7 @@ Polymer_PropertyEffects.prototype._createReadOnlyProperty = function(property, p
 Polymer_PropertyEffects.prototype._createPropertyObserver = function(property, method, dynamicFn){};
 /**
 * @param {string} expression Method expression
-* @param {(boolean|Object)=} dynamicFn Boolean or object map indicating
+* @param {(boolean | Object)=} dynamicFn Boolean or object map indicating
   whether method names should be included as a dependency to the effect.
 * @return {void}
 */
@@ -610,7 +631,7 @@ Polymer_PropertyEffects.prototype._createReflectedProperty = function(property){
 /**
 * @param {string} property Name of computed property to set
 * @param {string} expression Method expression
-* @param {(boolean|Object)=} dynamicFn Boolean or object map indicating
+* @param {(boolean | Object)=} dynamicFn Boolean or object map indicating
   whether method names should be included as a dependency to the effect.
 * @return {void}
 */
@@ -667,7 +688,7 @@ Polymer_PropertyEffects._parseTemplateNodeAttribute = function(node, templateInf
 Polymer_PropertyEffects.addPropertyEffect = function(property, type, effect){};
 /**
 * @param {string} property Property name
-* @param {(string|function (*, *))} method Function or name of observer method to call
+* @param {(string | function (*, *))} method Function or name of observer method to call
 * @param {boolean=} dynamicFn Whether the method name should be included as
   a dependency to the effect.
 * @return {void}
@@ -675,7 +696,7 @@ Polymer_PropertyEffects.addPropertyEffect = function(property, type, effect){};
 Polymer_PropertyEffects.createPropertyObserver = function(property, method, dynamicFn){};
 /**
 * @param {string} expression Method expression
-* @param {(boolean|Object)=} dynamicFn Boolean or object map indicating
+* @param {(boolean | Object)=} dynamicFn Boolean or object map indicating
 * @return {void}
 */
 Polymer_PropertyEffects.createMethodObserver = function(expression, dynamicFn){};
@@ -699,7 +720,7 @@ Polymer_PropertyEffects.createReflectedProperty = function(property){};
 /**
 * @param {string} property Name of computed property to set
 * @param {string} expression Method expression
-* @param {(boolean|Object)=} dynamicFn Boolean or object map indicating whether
+* @param {(boolean | Object)=} dynamicFn Boolean or object map indicating whether
   method names should be included as a dependency to the effect.
 * @return {void}
 */
@@ -741,14 +762,15 @@ Polymer_PropertyEffects._evaluateBinding = function(inst, part, path, props, old
 function Polymer_PropertiesMixin(){}
 /**
 * @override
+* @return {void}
 */
 Polymer_PropertiesMixin.prototype._initializeProperties = function(){};
 /**
-* @return {undefined}
+* @return {void}
 */
 Polymer_PropertiesMixin.prototype.connectedCallback = function(){};
 /**
-* @return {undefined}
+* @return {void}
 */
 Polymer_PropertiesMixin.prototype.disconnectedCallback = function(){};
 /**
@@ -782,7 +804,7 @@ Polymer_ElementMixin.prototype.rootPath;
 /** @type {string} */
 Polymer_ElementMixin.prototype.importPath;
 
-/** @type {(StampedTemplate|HTMLElement|ShadowRoot)} */
+/** @type {(StampedTemplate | HTMLElement | ShadowRoot)} */
 Polymer_ElementMixin.prototype.root;
 
 /** @type {!Object.<string, !Element>} */
@@ -790,18 +812,21 @@ Polymer_ElementMixin.prototype.$;
 
 /**
 * @override
+* @return {void}
 */
 Polymer_ElementMixin.prototype.ready = function(){};
 /**
 * @override
+* @return {void}
 */
 Polymer_ElementMixin.prototype._initializeProperties = function(){};
 /**
 * @override
+* @return {void}
 */
 Polymer_ElementMixin.prototype._readyClients = function(){};
 /**
-* @return {undefined}
+* @return {void}
 */
 Polymer_ElementMixin.prototype.connectedCallback = function(){};
 /**
@@ -861,15 +886,17 @@ Polymer_ElementMixin._finalizeTemplate = function(is){};
 */
 function Polymer_GestureEventListeners(){}
 /**
-* @param {*} node 
-* @param {*} eventName 
-* @param {*} handler 
+* @param {!Node} node Node to add event listener to
+* @param {string} eventName Name of event
+* @param {Function} handler Listener function to add
+* @return {void}
 */
 Polymer_GestureEventListeners.prototype._addEventListenerToNode = function(node, eventName, handler){};
 /**
-* @param {*} node 
-* @param {*} eventName 
-* @param {*} handler 
+* @param {!Node} node Node to remove event listener from
+* @param {string} eventName Name of event
+* @param {Function} handler Listener function to remove
+* @return {void}
 */
 Polymer_GestureEventListeners.prototype._removeEventListenerFromNode = function(node, eventName, handler){};
 /**
@@ -881,15 +908,15 @@ function Polymer_DirMixin(){}
 Polymer_DirMixin.prototype.__autoDirOptOut;
 
 /**
-* @return {undefined}
+* @return {void}
 */
 Polymer_DirMixin.prototype.ready = function(){};
 /**
-* @return {undefined}
+* @return {void}
 */
 Polymer_DirMixin.prototype.connectedCallback = function(){};
 /**
-* @return {undefined}
+* @return {void}
 */
 Polymer_DirMixin.prototype.disconnectedCallback = function(){};
 /**
@@ -918,10 +945,12 @@ Polymer_LegacyElementMixin.prototype._debouncers;
 
 /**
 * @override
+* @return {void}
 */
 Polymer_LegacyElementMixin.prototype.ready = function(){};
 /**
 * @override
+* @return {void}
 */
 Polymer_LegacyElementMixin.prototype._initializeProperties = function(){};
 /**
@@ -929,49 +958,53 @@ Polymer_LegacyElementMixin.prototype._initializeProperties = function(){};
 * @param {string} name Name of attribute.
 * @param {?string} old Old value of attribute.
 * @param {?string} value Current value of attribute.
+* @return {void}
 */
 Polymer_LegacyElementMixin.prototype.attributeChangedCallback = function(name, old, value){};
 /**
 * @override
+* @return {void}
 */
 Polymer_LegacyElementMixin.prototype.connectedCallback = function(){};
 /**
 * @override
+* @return {void}
 */
 Polymer_LegacyElementMixin.prototype.disconnectedCallback = function(){};
 /**
-* @return {undefined}
+* @return {void}
 */
 Polymer_LegacyElementMixin.prototype.created = function(){};
 /**
-* @return {undefined}
+* @return {void}
 */
 Polymer_LegacyElementMixin.prototype.attached = function(){};
 /**
-* @return {undefined}
+* @return {void}
 */
 Polymer_LegacyElementMixin.prototype.detached = function(){};
 /**
 * @param {string} name Name of attribute.
 * @param {?string} old Old value of attribute.
 * @param {?string} value Current value of attribute.
+* @return {void}
 */
 Polymer_LegacyElementMixin.prototype.attributeChanged = function(name, old, value){};
 /**
-* @return {undefined}
+* @return {void}
 */
 Polymer_LegacyElementMixin.prototype._registered = function(){};
 /**
-* @return {undefined}
+* @return {void}
 */
 Polymer_LegacyElementMixin.prototype._ensureAttributes = function(){};
 /**
-* @return {undefined}
+* @return {void}
 */
 Polymer_LegacyElementMixin.prototype._applyListeners = function(){};
 /**
 * @param {*} value Value to deserialize
-* @return {(string|undefined)}
+* @return {(string | undefined)}
 */
 Polymer_LegacyElementMixin.prototype.serialize = function(value){};
 /**
@@ -1022,7 +1055,7 @@ Polymer_LegacyElementMixin.prototype.instanceTemplate = function(template){};
 * @param {string} type Name of event type.
 * @param {*=} detail Detail value containing event-specific
   payload.
-* @param {{bubbles: (boolean|undefined), cancelable: (boolean|undefined), composed: (boolean|undefined)}=} options Object specifying options.  These may include:
+* @param {{bubbles: (boolean | undefined), cancelable: (boolean | undefined), composed: (boolean | undefined)}=} options Object specifying options.  These may include:
  `bubbles` (boolean, defaults to `true`),
  `cancelable` (boolean, defaults to false), and
  `node` on which to fire the event (HTMLElement, defaults to `this`).
@@ -1062,16 +1095,16 @@ Polymer_LegacyElementMixin.prototype.$$ = function(slctr){};
 */
 Polymer_LegacyElementMixin.prototype.distributeContent = function(){};
 /**
-* @return {Array.<Node>}
+* @return {!Array.<!Node>}
 */
 Polymer_LegacyElementMixin.prototype.getEffectiveChildNodes = function(){};
 /**
 * @param {string} selector Selector to run.
-* @return {Array.<Node>}
+* @return {!Array.<!Node>}
 */
 Polymer_LegacyElementMixin.prototype.queryDistributedElements = function(selector){};
 /**
-* @return {Array.<Node>}
+* @return {!Array.<!Node>}
 */
 Polymer_LegacyElementMixin.prototype.getEffectiveChildren = function(){};
 /**
@@ -1085,19 +1118,19 @@ Polymer_LegacyElementMixin.prototype.getEffectiveTextContent = function(){};
 Polymer_LegacyElementMixin.prototype.queryEffectiveChildren = function(selector){};
 /**
 * @param {string} selector Selector to run.
-* @return {Array.<Node>}
+* @return {!Array.<!Node>}
 */
 Polymer_LegacyElementMixin.prototype.queryAllEffectiveChildren = function(selector){};
 /**
 * @param {string=} slctr CSS selector to choose the desired
   `<slot>`.  Defaults to `content`.
-* @return {Array.<Node>}
+* @return {!Array.<!Node>}
 */
 Polymer_LegacyElementMixin.prototype.getContentChildNodes = function(slctr){};
 /**
 * @param {string=} slctr CSS selector to choose the desired
   `<content>`.  Defaults to `content`.
-* @return {Array.<HTMLElement>}
+* @return {!Array.<!HTMLElement>}
 */
 Polymer_LegacyElementMixin.prototype.getContentChildren = function(slctr){};
 /**
@@ -1111,8 +1144,9 @@ Polymer_LegacyElementMixin.prototype.isLightDescendant = function(node){};
 */
 Polymer_LegacyElementMixin.prototype.isLocalDescendant = function(node){};
 /**
-* @param {*} container 
-* @param {*} shouldObserve 
+* @param {*} container Unused
+* @param {*} shouldObserve Unused
+* @return {void}
 */
 Polymer_LegacyElementMixin.prototype.scopeSubtree = function(container, shouldObserve){};
 /**
@@ -1122,7 +1156,7 @@ Polymer_LegacyElementMixin.prototype.scopeSubtree = function(container, shouldOb
 Polymer_LegacyElementMixin.prototype.getComputedStyleValue = function(property){};
 /**
 * @param {string} jobName String to identify the debounce job.
-* @param {function ()} callback Function that is called (with `this`
+* @param {function (): void} callback Function that is called (with `this`
   context) when the wait time elapses.
 * @param {number} wait Optional wait time in milliseconds (ms) after the
   last signal that must elapse before invoking `callback`
@@ -1173,7 +1207,7 @@ Polymer_LegacyElementMixin.prototype.create = function(tag, props){};
   unsuccessfully loaded.
 * @param {boolean=} optAsync True if the import should be loaded `async`.
   Defaults to `false`.
-* @return {HTMLLinkElement}
+* @return {!HTMLLinkElement}
 */
 Polymer_LegacyElementMixin.prototype.importHref = function(href, onload, onerror, optAsync){};
 /**
@@ -1187,6 +1221,7 @@ Polymer_LegacyElementMixin.prototype.elementMatches = function(selector, node){}
 * @param {boolean=} bool Boolean to force the attribute on or off.
    When unspecified, the state of the attribute will be reversed.
 * @param {Element=} node Node to target.  Defaults to `this`.
+* @return {void}
 */
 Polymer_LegacyElementMixin.prototype.toggleAttribute = function(name, bool, node){};
 /**
@@ -1194,6 +1229,7 @@ Polymer_LegacyElementMixin.prototype.toggleAttribute = function(name, bool, node
 * @param {boolean=} bool Boolean to force the class on or off.
    When unspecified, the state of the class will be reversed.
 * @param {Element=} node Node to target.  Defaults to `this`.
+* @return {void}
 */
 Polymer_LegacyElementMixin.prototype.toggleClass = function(name, bool, node){};
 /**
@@ -1213,7 +1249,7 @@ Defaults to `this`.
 */
 Polymer_LegacyElementMixin.prototype.translate3d = function(x, y, z, node){};
 /**
-* @param {(string|!Array.<(number|string)>)} arrayOrPath Path to array from which to remove the item
+* @param {(string | !Array.<(number | string)>)} arrayOrPath Path to array from which to remove the item
   (or the array itself).
 * @param {*} item Item to remove.
 * @return {Array}
@@ -1222,23 +1258,27 @@ Polymer_LegacyElementMixin.prototype.arrayDelete = function(arrayOrPath, item){}
 /**
 * @param {string} level One of 'log', 'warn', 'error'
 * @param {Array} args Array of strings or objects to log
+* @return {void}
 */
 Polymer_LegacyElementMixin.prototype._logger = function(level, args){};
 /**
-* @param {...*} args 
+* @param {...*} args Array of strings or objects to log
+* @return {void}
 */
 Polymer_LegacyElementMixin.prototype._log = function(args){};
 /**
-* @param {...*} args 
+* @param {...*} args Array of strings or objects to log
+* @return {void}
 */
 Polymer_LegacyElementMixin.prototype._warn = function(args){};
 /**
-* @param {...*} args 
+* @param {...*} args Array of strings or objects to log
+* @return {void}
 */
 Polymer_LegacyElementMixin.prototype._error = function(args){};
 /**
 * @param {string} methodName Method name to associate with message
-* @param {...*} args 
+* @param {...*} args Array of strings or objects to log
 * @return {Array}
 */
 Polymer_LegacyElementMixin.prototype._logf = function(methodName, args){};
@@ -1278,7 +1318,7 @@ Polymer_ArraySelectorMixin.prototype.items;
 /** @type {boolean} */
 Polymer_ArraySelectorMixin.prototype.multi;
 
-/** @type {?(Object|Array.<!Object>)} */
+/** @type {?(Object | Array.<!Object>)} */
 Polymer_ArraySelectorMixin.prototype.selected;
 
 /** @type {?Object} */
@@ -1288,7 +1328,7 @@ Polymer_ArraySelectorMixin.prototype.selectedItem;
 Polymer_ArraySelectorMixin.prototype.toggle;
 
 /**
-* @return {undefined}
+* @return {void}
 */
 Polymer_ArraySelectorMixin.prototype.clearSelection = function(){};
 /**
@@ -1320,4 +1360,4 @@ Polymer_ArraySelectorMixin.prototype.select = function(item){};
 * @param {number} idx Index from `items` array to select
 * @return {void}
 */
-Polymer_ArraySelectorMixin.prototype.selectIndex = function(idx){};
+Polymer_ArraySelectorMixin.prototype.selectIndex = function(idx){};
\ No newline at end of file
diff --git a/externs/polymer-internal-shared-types.js b/externs/polymer-internal-shared-types.js
index 525aaae7a1..274f60351d 100644
--- a/externs/polymer-internal-shared-types.js
+++ b/externs/polymer-internal-shared-types.js
@@ -161,5 +161,5 @@ let TemplatizeOptions;
 function AsyncInterface(){}
 /** @type {function(!Function, number=): number} */
 AsyncInterface.prototype.run;
-/** @type {function(number)} */
-AsyncInterface.prototype.cancel;
\ No newline at end of file
+/** @type {function(number): void} */
+AsyncInterface.prototype.cancel;
diff --git a/gulpfile.js b/gulpfile.js
index ab3ff6028c..e705fa5832 100644
--- a/gulpfile.js
+++ b/gulpfile.js
@@ -113,7 +113,7 @@ class AddClosureTypeImport extends Transform {
 
 gulp.task('clean', () => del([DIST_DIR, 'closure.log']));
 
-gulp.task('closure', ['clean'], () => {
+gulp.task('closure', ['generate-externs'], () => {
 
   let entry, splitRx, joinRx, addClosureTypes;
 
diff --git a/lib/elements/dom-if.html b/lib/elements/dom-if.html
index 9da7f11356..d6ad8ca736 100644
--- a/lib/elements/dom-if.html
+++ b/lib/elements/dom-if.html
@@ -117,6 +117,9 @@
       Polymer.enqueueDebouncer(this.__renderDebouncer);
     }
 
+    /**
+     * @return {void}
+     */
     disconnectedCallback() {
       super.disconnectedCallback();
       if (!this.parentNode ||
@@ -126,6 +129,9 @@
       }
     }
 
+    /**
+     * @return {void}
+     */
     connectedCallback() {
       super.connectedCallback();
       this.style.display = 'none';
@@ -258,6 +264,13 @@
       }
     }
 
+    /**
+     * Shows or hides the template instance top level child elements. For
+     * text nodes, `textContent` is removed while "hidden" and replaced when
+     * "shown."
+     * @return {void}
+     * @protected
+     */
     _showHideChildren() {
       let hidden = this.__hideTemplateChildren__ || !this.if;
       if (this.__instance) {
diff --git a/lib/elements/dom-repeat.html b/lib/elements/dom-repeat.html
index ec62e6a87c..01b2e1a726 100644
--- a/lib/elements/dom-repeat.html
+++ b/lib/elements/dom-repeat.html
@@ -296,6 +296,9 @@
       this.template = null;
     }
 
+    /**
+     * @return {void}
+     */
     disconnectedCallback() {
       super.disconnectedCallback();
       this.__isDetached = true;
@@ -304,6 +307,9 @@
       }
     }
 
+    /**
+     * @return {void}
+     */
     connectedCallback() {
       super.connectedCallback();
       this.style.display = 'none';
@@ -617,6 +623,15 @@
     }
 
     // Implements extension point from Templatize mixin
+    /**
+     * Shows or hides the template instance top level child elements. For
+     * text nodes, `textContent` is removed while "hidden" and replaced when
+     * "shown."
+     * @param {boolean} hidden Set to true to hide the children;
+     * set to false to show them.
+     * @return {void}
+     * @protected
+     */
     _showHideChildren(hidden) {
       for (let i=0; i<this.__instances.length; i++) {
         this.__instances[i]._showHideChildren(hidden);
diff --git a/lib/legacy/class.html b/lib/legacy/class.html
index d2e0fc1110..fb8e89564b 100644
--- a/lib/legacy/class.html
+++ b/lib/legacy/class.html
@@ -167,6 +167,9 @@
             null;
         }
 
+        /**
+         * @return {void}
+         */
         created() {
           super.created();
           if (info.created) {
@@ -174,6 +177,9 @@
           }
         }
 
+        /**
+         * @return {void}
+         */
         _registered() {
           super._registered();
           /* NOTE: `beforeRegister` is called here for bc, but the behavior
@@ -191,6 +197,9 @@
           }
         }
 
+        /**
+         * @return {void}
+         */
         _applyListeners() {
           super._applyListeners();
           if (info.listeners) {
@@ -203,6 +212,9 @@
         // note: exception to "super then me" rule;
         // do work before calling super so that super attributes
         // only apply if not already set.
+        /**
+         * @return {void}
+         */
         _ensureAttributes() {
           if (info.hostAttributes) {
             for (let a in info.hostAttributes) {
@@ -212,6 +224,9 @@
           super._ensureAttributes();
         }
 
+        /**
+         * @return {void}
+         */
         ready() {
           super.ready();
           if (info.ready) {
@@ -219,6 +234,9 @@
           }
         }
 
+        /**
+         * @return {void}
+         */
         attached() {
           super.attached();
           if (info.attached) {
@@ -226,6 +244,9 @@
           }
         }
 
+        /**
+         * @return {void}
+         */
         detached() {
           super.detached();
           if (info.detached) {
@@ -233,6 +254,15 @@
           }
         }
 
+        /**
+         * Implements native Custom Elements `attributeChangedCallback` to
+         * set an attribute value to a property via `_attributeToProperty`.
+         *
+         * @param {string} name Name of attribute that changed
+         * @param {?string} old Old attribute value
+         * @param {?string} value New attribute value
+         * @return {void}
+         */
         attributeChanged(name, old, value) {
           super.attributeChanged(name, old, value);
           if (info.attributeChanged) {
diff --git a/lib/legacy/legacy-element-mixin.html b/lib/legacy/legacy-element-mixin.html
index 4f912b8a8d..b8855d2e2d 100644
--- a/lib/legacy/legacy-element-mixin.html
+++ b/lib/legacy/legacy-element-mixin.html
@@ -91,12 +91,14 @@
       /**
        * Legacy callback called during the `constructor`, for overriding
        * by the user.
+       * @return {void}
        */
       created() {}
 
       /**
        * Provides an implementation of `connectedCallback`
        * which adds Polymer legacy API's `attached` method.
+       * @return {void}
        * @override
        */
       connectedCallback() {
@@ -108,12 +110,14 @@
       /**
        * Legacy callback called during `connectedCallback`, for overriding
        * by the user.
+       * @return {void}
        */
       attached() {}
 
       /**
        * Provides an implementation of `disconnectedCallback`
        * which adds Polymer legacy API's `detached` method.
+       * @return {void}
        * @override
        */
       disconnectedCallback() {
@@ -125,6 +129,7 @@
       /**
        * Legacy callback called during `disconnectedCallback`, for overriding
        * by the user.
+       * @return {void}
        */
       detached() {}
 
@@ -150,6 +155,7 @@
        * @param {string} name Name of attribute.
        * @param {?string} old Old value of attribute.
        * @param {?string} value Current value of attribute.
+       * @return {void}
        */
       attributeChanged(name, old, value) {} // eslint-disable-line no-unused-vars
 
@@ -158,6 +164,7 @@
        * add support for class initialization via the `_registered` callback.
        * This is called only when the first instance of the element is created.
        *
+       * @return {void}
        * @override
        */
       _initializeProperties() {
@@ -175,6 +182,7 @@
        * work. The implementation should ensure the work is performed
        * only once for the class.
        * @protected
+       * @return {void}
        */
       _registered() {}
 
@@ -182,6 +190,7 @@
        * Overrides the default `Polymer.PropertyEffects` implementation to
        * add support for installing `hostAttributes` and `listeners`.
        *
+       * @return {void}
        * @override
        */
       ready() {
@@ -198,6 +207,7 @@
        * to the element user and not done here; reasonable exceptions include
        * setting aria roles and focusability.
        * @protected
+       * @return {void}
        */
       _ensureAttributes() {}
 
@@ -210,6 +220,7 @@
        * these elements, consider adding listeners asynchronously so as not to
        * block render.
        * @protected
+       * @return {void}
        */
       _applyListeners() {}
 
@@ -627,7 +638,13 @@
         return this.root === node.getRootNode();
       }
 
-      // NOTE: should now be handled by ShadyCss library.
+      /**
+       * No-op for backwards compatibility. This should now be handled by
+       * ShadyCss library.
+       * @param  {*} container Unused
+       * @param  {*} shouldObserve Unused
+       * @return {void}
+       */
       scopeSubtree(container, shouldObserve) { // eslint-disable-line no-unused-vars
       }
 
@@ -811,6 +828,7 @@
        * @param {boolean=} bool Boolean to force the attribute on or off.
        *    When unspecified, the state of the attribute will be reversed.
        * @param {Element=} node Node to target.  Defaults to `this`.
+       * @return {void}
        */
       toggleAttribute(name, bool, node) {
         node = /** @type {Element} */ (node || this);
@@ -832,6 +850,7 @@
        * @param {boolean=} bool Boolean to force the class on or off.
        *    When unspecified, the state of the class will be reversed.
        * @param {Element=} node Node to target.  Defaults to `this`.
+       * @return {void}
        */
       toggleClass(name, bool, node) {
         node = /** @type {Element} */ (node || this);
@@ -914,6 +933,7 @@
        *
        * @param {string} level One of 'log', 'warn', 'error'
        * @param {Array} args Array of strings or objects to log
+       * @return {void}
        */
       _logger(level, args) {
         // accept ['foo', 'bar'] and [['foo', 'bar']]
@@ -932,6 +952,7 @@
        * Facades `console.log` as an override point.
        *
        * @param {...*} args Array of strings or objects to log
+       * @return {void}
        */
       _log(...args) {
         this._logger('log', args);
@@ -941,6 +962,7 @@
        * Facades `console.warn` as an override point.
        *
        * @param {...*} args Array of strings or objects to log
+       * @return {void}
        */
       _warn(...args) {
         this._logger('warn', args);
@@ -950,6 +972,7 @@
        * Facades `console.error` as an override point.
        *
        * @param {...*} args Array of strings or objects to log
+       * @return {void}
        */
       _error(...args) {
         this._logger('error', args);
diff --git a/lib/mixins/dir-mixin.html b/lib/mixins/dir-mixin.html
index 773870d575..68db35d5fe 100644
--- a/lib/mixins/dir-mixin.html
+++ b/lib/mixins/dir-mixin.html
@@ -134,13 +134,17 @@
 
         /**
          * @suppress {invalidCasts} Closure doesn't understand that `this` is an HTMLElement
+         * @return {void}
          */
         ready() {
           super.ready();
           this.__autoDirOptOut = /** @type {!HTMLElement} */(this).hasAttribute('dir');
         }
 
-        /** @suppress {missingProperties} If it exists on elementBase, it can be super'd */
+        /**
+         * @suppress {missingProperties} If it exists on elementBase, it can be super'd
+         * @return {void}
+         */
         connectedCallback() {
           if (elementBase.prototype.connectedCallback) {
             super.connectedCallback();
@@ -152,7 +156,10 @@
           }
         }
 
-        /** @suppress {missingProperties} If it exists on elementBase, it can be super'd */
+        /**
+         * @suppress {missingProperties} If it exists on elementBase, it can be super'd
+         * @return {void}
+         */
         disconnectedCallback() {
           if (elementBase.prototype.disconnectedCallback) {
             super.disconnectedCallback();
@@ -171,4 +178,4 @@
       return Dir;
     });
   })();
-</script>
\ No newline at end of file
+</script>
diff --git a/lib/mixins/element-mixin.html b/lib/mixins/element-mixin.html
index fa983bddd6..0a4c930145 100644
--- a/lib/mixins/element-mixin.html
+++ b/lib/mixins/element-mixin.html
@@ -443,6 +443,7 @@
        * It also initializes any property defaults provided via `value` in
        * `properties` metadata.
        *
+       * @return {void}
        * @override
        * @suppress {invalidCasts}
        */
@@ -525,6 +526,7 @@
        * when using the ShadyCSS scoping/custom properties polyfill.
        *
        * @suppress {missingProperties, invalidCasts} Super may or may not implement the callback
+       * @return {void}
        */
       connectedCallback() {
         if (window.ShadyCSS && this._template) {
@@ -536,6 +538,7 @@
       /**
        * Stamps the element template.
        *
+       * @return {void}
        * @override
        */
       ready() {
@@ -553,6 +556,7 @@
        * client dom to be attached to the element prior to any observers
        * running.
        *
+       * @return {void}
        * @override
        */
       _readyClients() {
diff --git a/lib/mixins/gesture-event-listeners.html b/lib/mixins/gesture-event-listeners.html
index 1a63efa182..105e2fade3 100644
--- a/lib/mixins/gesture-event-listeners.html
+++ b/lib/mixins/gesture-event-listeners.html
@@ -45,12 +45,28 @@
      */
     class GestureEventListeners extends superClass {
 
+      /**
+       * Add the event listener to the node if it is a gestures event.
+       *
+       * @param {!Node} node Node to add event listener to
+       * @param {string} eventName Name of event
+       * @param {Function} handler Listener function to add
+       * @return {void}
+       */
       _addEventListenerToNode(node, eventName, handler) {
         if (!gestures.addListener(node, eventName, handler)) {
           super._addEventListenerToNode(node, eventName, handler);
         }
       }
 
+      /**
+       * Remove the event listener to the node if it is a gestures event.
+       *
+       * @param {!Node} node Node to remove event listener from
+       * @param {string} eventName Name of event
+       * @param {Function} handler Listener function to remove
+       * @return {void}
+       */
       _removeEventListenerFromNode(node, eventName, handler) {
         if (!gestures.removeListener(node, eventName, handler)) {
           super._removeEventListenerFromNode(node, eventName, handler);
diff --git a/lib/mixins/properties-changed.html b/lib/mixins/properties-changed.html
index 195ffc8cde..066f572d95 100644
--- a/lib/mixins/properties-changed.html
+++ b/lib/mixins/properties-changed.html
@@ -103,6 +103,7 @@
          * @param {string} property Name of the property
          * @param {boolean=} readOnly When true, no setter is created; the
          *   protected `_setProperty` function must be used to set the property
+         * @return {void}
          * @protected
          */
         _createPropertyAccessor(property, readOnly) {
@@ -124,6 +125,7 @@
          * Defines a property accessor for the given property.
          * @param {string} property Name of the property
          * @param {boolean=} readOnly When true, no setter is created
+         * @return {void}
          */
          _definePropertyAccessor(property, readOnly) {
           Object.defineProperty(this, property, {
@@ -164,6 +166,7 @@
          * bindings.  `super.ready()` must be called to ensure the data system
          * becomes enabled.
          *
+         * @return {void}
          * @public
          */
         ready() {
@@ -177,6 +180,7 @@
          * Provided as an override point for performing any setup work prior
          * to initializing the property accessor system.
          *
+         * @return {void}
          * @protected
          */
         _initializeProperties() {
@@ -202,6 +206,7 @@
          *
          * @param {Object} props Bag of property values that were overwritten
          *   when creating property accessors.
+         * @return {void}
          * @protected
          */
         _initializeInstanceProperties(props) {
@@ -214,6 +219,7 @@
          *
          * @param {string} property Name of the property
          * @param {*} value Value to set
+         * @return {void}
          * @protected
          */
         _setProperty(property, value) {
@@ -268,6 +274,7 @@
          * Marks the properties as invalid, and enqueues an async
          * `_propertiesChanged` callback.
          *
+         * @return {void}
          * @protected
          */
         _invalidateProperties() {
@@ -290,6 +297,7 @@
          * It is safe to call this method multiple times as it only turns on
          * property accessors once.
          *
+         * @return {void}
          * @protected
          */
         _enableProperties() {
@@ -309,7 +317,7 @@
          * set), and resets the pending set of changes. Generally, this method
          * should not be called in user code.
          *
-         *
+         * @return {void}
          * @protected
          */
         _flushProperties() {
@@ -329,6 +337,7 @@
          *   call to `_propertiesChanged`
          * @param {!Object} oldProps Bag of previous values for each property
          *   in `changedProps`
+         * @return {void}
          * @protected
          */
         _propertiesChanged(currentProps, changedProps, oldProps) { // eslint-disable-line no-unused-vars
@@ -369,6 +378,7 @@
          * @param {string} name Name of attribute that changed
          * @param {?string} old Old attribute value
          * @param {?string} value New attribute value
+         * @return {void}
          * @suppress {missingProperties} Super may or may not implement the callback
          */
         attributeChangedCallback(name, old, value) {
@@ -390,6 +400,7 @@
          * @param {?string} value of the attribute.
          * @param {*=} type type to deserialize to, defaults to the value
          * returned from `typeForProperty`
+         * @return {void}
          */
         _attributeToProperty(attribute, value, type) {
           if (!this.__serializing) {
@@ -408,6 +419,7 @@
          * @param {string} property Property name to reflect.
          * @param {string=} attribute Attribute name to reflect to.
          * @param {*=} value Property value to refect.
+         * @return {void}
          */
         _propertyToAttribute(property, attribute, value) {
           this.__serializing = true;
@@ -428,6 +440,7 @@
          * @param {Element} node Element to set attribute to.
          * @param {*} value Value to serialize.
          * @param {string} attribute Attribute name to serialize to.
+         * @return {void}
          */
         _valueToNodeAttribute(node, value, attribute) {
           const str = this._serializeValue(value);
@@ -490,4 +503,4 @@
 
   })();
 
-</script>
\ No newline at end of file
+</script>
diff --git a/lib/mixins/properties-mixin.html b/lib/mixins/properties-mixin.html
index 2298799b1d..ec069f26e6 100644
--- a/lib/mixins/properties-mixin.html
+++ b/lib/mixins/properties-mixin.html
@@ -181,6 +181,7 @@
        * Overrides `PropertiesChanged` method and adds a call to
        * `finalize` which lazily configures the element's property accessors.
        * @override
+       * @return {void}
        */
       _initializeProperties() {
         this.constructor.finalize();
@@ -192,6 +193,7 @@
        * Calls `_enableProperties` to turn on property system from
        * `PropertiesChanged`.
        * @suppress {missingProperties} Super may or may not implement the callback
+       * @return {void}
        */
       connectedCallback() {
         if (super.connectedCallback) {
@@ -203,6 +205,7 @@
       /**
        * Called when the element is removed from a document
        * @suppress {missingProperties} Super may or may not implement the callback
+       * @return {void}
        */
       disconnectedCallback() {
         if (super.disconnectedCallback) {
diff --git a/lib/mixins/property-effects.html b/lib/mixins/property-effects.html
index 8c26892f02..8b2fc689a4 100644
--- a/lib/mixins/property-effects.html
+++ b/lib/mixins/property-effects.html
@@ -1180,6 +1180,9 @@
         return TYPES;
       }
 
+      /**
+       * @return {void}
+       */
       _initializeProperties() {
         super._initializeProperties();
         hostStack.registerHost(this);
@@ -1202,6 +1205,7 @@
        *
        * @override
        * @param {Object} props Properties to initialize on the prototype
+       * @return {void}
        */
       _initializeProtoProperties(props) {
         this.__data = Object.create(props);
@@ -1215,6 +1219,7 @@
        *
        * @override
        * @param {Object} props Properties to initialize on the instance
+       * @return {void}
        */
       _initializeInstanceProperties(props) {
         let readOnly = this[TYPES.READ_ONLY];
@@ -1494,6 +1499,9 @@
        * to true, for per-property notification tracking.
        *
        * @override
+       * @param {string} property Name of the property
+       * @param {*} value Value to set
+       * @return {void}
        */
       _setProperty(property, value) {
         if (this._setPendingProperty(property, value, true)) {
@@ -1508,6 +1516,7 @@
        * `_propertiesChanged` synchronously.
        *
        * @override
+       * @return {void}
        */
       _invalidateProperties() {
         if (this.__dataReady) {
@@ -1534,6 +1543,7 @@
       /**
        * Overrides superclass implementation.
        *
+       * @return {void}
        * @protected
        */
       _flushProperties() {
@@ -1636,6 +1646,7 @@
        * that was not enabled as a result of flushing properties.
        *
        * @override
+       * @return {void}
        */
       ready() {
         // It is important that `super.ready()` is not called here as it
@@ -1661,7 +1672,12 @@
        * Runs each class of effects for the batch of changed properties in
        * a specific order (compute, propagate, reflect, observe, notify).
        *
-       * @override
+       * @param {!Object} currentProps Bag of all current accessor values
+       * @param {!Object} changedProps Bag of properties changed since the last
+       *   call to `_propertiesChanged`
+       * @param {!Object} oldProps Bag of previous values for each property
+       *   in `changedProps`
+       * @return {void}
        */
       _propertiesChanged(currentProps, changedProps, oldProps) {
         // ----------------------------
diff --git a/lib/mixins/template-stamp.html b/lib/mixins/template-stamp.html
index a8cf993534..fd01f406b3 100644
--- a/lib/mixins/template-stamp.html
+++ b/lib/mixins/template-stamp.html
@@ -443,7 +443,7 @@
        * This method generates a handler function that looks up the method
        * name at handling time.
        *
-       * @param {Node} node Node to add listener on
+       * @param {!Node} node Node to add listener on
        * @param {string} eventName Name of event
        * @param {string} methodName Name of method
        * @param {*=} context Context the method will be called on (defaults
@@ -460,7 +460,7 @@
       /**
        * Override point for adding custom or simulated event handling.
        *
-       * @param {Node} node Node to add event listener to
+       * @param {!Node} node Node to add event listener to
        * @param {string} eventName Name of event
        * @param {Function} handler Listener function to add
        * @return {void}
diff --git a/lib/utils/flattened-nodes-observer.html b/lib/utils/flattened-nodes-observer.html
index 9ea217fc70..e08d08cab3 100644
--- a/lib/utils/flattened-nodes-observer.html
+++ b/lib/utils/flattened-nodes-observer.html
@@ -16,7 +16,7 @@
 
   /**
    * Returns true if `node` is a slot element
-   * @param {HTMLElement} node Node to test.
+   * @param {Node} node Node to test.
    * @return {boolean} Returns true if the given `node` is a slot
    * @private
    */
@@ -97,7 +97,7 @@
     }
 
     /**
-     * @param {Node} target Node on which to listen for changes.
+     * @param {Element} target Node on which to listen for changes.
      * @param {Function} callback Function called when there are additions
      * or removals from the target's list of flattened nodes.
     */
@@ -113,6 +113,10 @@
        */
       this._nativeChildrenObserver = null;
       this._connected = false;
+      /**
+       * @type {Element}
+       * @private
+       */
       this._target = target;
       this.callback = callback;
       this._effectiveNodes = [];
@@ -181,6 +185,10 @@
       this._connected = false;
     }
 
+    /**
+     * @return {void}
+     * @private
+     */
     _schedule() {
       if (!this._scheduled) {
         this._scheduled = true;
@@ -188,11 +196,21 @@
       }
     }
 
+    /**
+     * @param {Array<MutationRecord>} mutations Mutations signaled by the mutation observer
+     * @return {void}
+     * @private
+     */
     _processMutations(mutations) {
       this._processSlotMutations(mutations);
       this.flush();
     }
 
+    /**
+     * @param {Array<MutationRecord>} mutations Mutations signaled by the mutation observer
+     * @return {void}
+     * @private
+     */
     _processSlotMutations(mutations) {
       if (mutations) {
         for (let i=0; i < mutations.length; i++) {
@@ -258,6 +276,11 @@
       return didFlush;
     }
 
+    /**
+     * @param {!Array<Element|Node>|!NodeList<Node>} nodeList Nodes that could change
+     * @return {void}
+     * @private
+     */
     _listenSlots(nodeList) {
       for (let i=0; i < nodeList.length; i++) {
         let n = nodeList[i];
@@ -267,6 +290,11 @@
       }
     }
 
+    /**
+     * @param {!Array<Element|Node>|!NodeList<Node>} nodeList Nodes that could change
+     * @return {void}
+     * @private
+     */
     _unlistenSlots(nodeList) {
       for (let i=0; i < nodeList.length; i++) {
         let n = nodeList[i];
diff --git a/lib/utils/gestures.html b/lib/utils/gestures.html
index 29353f835d..3fbba8a5fa 100644
--- a/lib/utils/gestures.html
+++ b/lib/utils/gestures.html
@@ -80,21 +80,21 @@
   let IS_TOUCH_ONLY = navigator.userAgent.match(/iP(?:[oa]d|hone)|Android/);
 
   let GestureRecognizer = function(){}; // eslint-disable-line no-unused-vars
-  /** @type {function()} */
+  /** @type {function(): void} */
   GestureRecognizer.prototype.reset;
-  /** @type {function(MouseEvent) | undefined} */
+  /** @type {function(MouseEvent): void | undefined} */
   GestureRecognizer.prototype.mousedown;
-  /** @type {(function(MouseEvent) | undefined)} */
+  /** @type {(function(MouseEvent): void | undefined)} */
   GestureRecognizer.prototype.mousemove;
-  /** @type {(function(MouseEvent) | undefined)} */
+  /** @type {(function(MouseEvent): void | undefined)} */
   GestureRecognizer.prototype.mouseup;
-  /** @type {(function(TouchEvent) | undefined)} */
+  /** @type {(function(TouchEvent): void | undefined)} */
   GestureRecognizer.prototype.touchstart;
-  /** @type {(function(TouchEvent) | undefined)} */
+  /** @type {(function(TouchEvent): void | undefined)} */
   GestureRecognizer.prototype.touchmove;
-  /** @type {(function(TouchEvent) | undefined)} */
+  /** @type {(function(TouchEvent): void | undefined)} */
   GestureRecognizer.prototype.touchend;
-  /** @type {(function(MouseEvent) | undefined)} */
+  /** @type {(function(MouseEvent): void | undefined)} */
   GestureRecognizer.prototype.click;
 
   // touch will make synthetic mouse events
diff --git a/lib/utils/templatize.html b/lib/utils/templatize.html
index 28810322f1..4f3b043721 100644
--- a/lib/utils/templatize.html
+++ b/lib/utils/templatize.html
@@ -123,8 +123,14 @@
           this.__dataHost._enqueueClient(this);
         }
       }
+
       /**
-       * @override
+       * Override point for adding custom or simulated event handling.
+       *
+       * @param {!Node} node Node to add event listener to
+       * @param {string} eventName Name of event
+       * @param {Function} handler Listener function to add
+       * @return {void}
        */
       _addEventListenerToNode(node, eventName, handler) {
         if (this._methodHost && this.__templatizeOptions.parentModel) {
@@ -185,7 +191,11 @@
        * textContent bindings while children are "hidden" and cache in
        * private storage for later retrieval.
        *
-       * @override
+       * @param {Node} node The node to set a property on
+       * @param {string} prop The property to set
+       * @param {*} value The value to set
+       * @return {void}
+       * @protected
        */
       _setUnmanagedPropertyToNode(node, prop, value) {
         if (node.__hideTemplateChildren__ &&
diff --git a/types/extra-types.d.ts b/types/extra-types.d.ts
index 60e147183d..36667de3aa 100644
--- a/types/extra-types.d.ts
+++ b/types/extra-types.d.ts
@@ -124,7 +124,7 @@ interface Binding {
 
 interface AsyncInterface {
   run: (fn: Function, delay?: number) => number;
-  cancel: (handle: number) => any;
+  cancel: (handle: number) => void;
 }
 
 /**
@@ -138,14 +138,14 @@ type AsyncModule = AsyncInterface;
  */
 
 interface GestureRecognizer {
-  reset: () => any;
-  mousedown?: (e: MouseEvent) => any;
-  mousemove?: (e: MouseEvent) => any;
-  mouseup?: (e: MouseEvent) => any;
-  touchstart?: (e: TouchEvent) => any;
-  touchmove?: (e: TouchEvent) => any;
-  touchend?: (e: TouchEvent) => any;
-  click?: (e: MouseEvent) => any;
+  reset: () => void;
+  mousedown?: (e: MouseEvent) => void;
+  mousemove?: (e: MouseEvent) => void;
+  mouseup?: (e: MouseEvent) => void;
+  touchstart?: (e: TouchEvent) => void;
+  touchmove?: (e: TouchEvent) => void;
+  touchend?: (e: TouchEvent) => void;
+  click?: (e: MouseEvent) => void;
 }
 
 /**
diff --git a/types/lib/elements/dom-if.d.ts b/types/lib/elements/dom-if.d.ts
index 7507dbee39..53348545d9 100644
--- a/types/lib/elements/dom-if.d.ts
+++ b/types/lib/elements/dom-if.d.ts
@@ -45,8 +45,8 @@ declare namespace Polymer {
      * in better performance.
      */
     restamp: boolean|null|undefined;
-    connectedCallback(): any;
-    disconnectedCallback(): any;
+    connectedCallback(): void;
+    disconnectedCallback(): void;
 
     /**
      * Forces the element to render its content. Normally rendering is
@@ -56,7 +56,13 @@ declare namespace Polymer {
      * validate application state.
      */
     render(): void;
-    _showHideChildren(): any;
+
+    /**
+     * Shows or hides the template instance top level child elements. For
+     * text nodes, `textContent` is removed while "hidden" and replaced when
+     * "shown."
+     */
+    _showHideChildren(): void;
   }
 }
 
diff --git a/types/lib/elements/dom-repeat.d.ts b/types/lib/elements/dom-repeat.d.ts
index 723c074c3c..4bf9b4d69b 100644
--- a/types/lib/elements/dom-repeat.d.ts
+++ b/types/lib/elements/dom-repeat.d.ts
@@ -201,8 +201,8 @@ declare namespace Polymer {
      */
     targetFramerate: number|null|undefined;
     _targetFrameTime: number|null|undefined;
-    disconnectedCallback(): any;
-    connectedCallback(): any;
+    disconnectedCallback(): void;
+    connectedCallback(): void;
 
     /**
      * Forces the element to render its content. Normally rendering is
@@ -214,9 +214,14 @@ declare namespace Polymer {
     render(): void;
 
     /**
-     * Implements extension point from Templatize mixin
+     * Shows or hides the template instance top level child elements. For
+     * text nodes, `textContent` is removed while "hidden" and replaced when
+     * "shown."
+     *
+     * @param hidden Set to true to hide the children;
+     * set to false to show them.
      */
-    _showHideChildren(hidden: any): any;
+    _showHideChildren(hidden: boolean): void;
 
     /**
      * Returns the item associated with a given element stamped by
diff --git a/types/lib/legacy/class.d.ts b/types/lib/legacy/class.d.ts
index 832e025dce..2068f0c42b 100644
--- a/types/lib/legacy/class.d.ts
+++ b/types/lib/legacy/class.d.ts
@@ -95,16 +95,21 @@ declare namespace Polymer {
 }
 
 declare class PolymerGenerated {
-  created(): any;
-  _registered(): any;
-  _applyListeners(): any;
+  created(): void;
+  _registered(): void;
+  _applyListeners(): void;
+  _ensureAttributes(): void;
+  ready(): void;
+  attached(): void;
+  detached(): void;
 
   /**
-   * only apply if not already set.
+   * Implements native Custom Elements `attributeChangedCallback` to
+   * set an attribute value to a property via `_attributeToProperty`.
+   *
+   * @param name Name of attribute that changed
+   * @param old Old attribute value
+   * @param value New attribute value
    */
-  _ensureAttributes(): any;
-  ready(): any;
-  attached(): any;
-  detached(): any;
-  attributeChanged(name: any, old: any, value: any): any;
+  attributeChanged(name: string, old: string|null, value: string|null): void;
 }
diff --git a/types/lib/legacy/legacy-element-mixin.d.ts b/types/lib/legacy/legacy-element-mixin.d.ts
index 70c69e317f..40ce35b64b 100644
--- a/types/lib/legacy/legacy-element-mixin.d.ts
+++ b/types/lib/legacy/legacy-element-mixin.d.ts
@@ -37,14 +37,14 @@ declare namespace Polymer {
      * Overrides the default `Polymer.PropertyEffects` implementation to
      * add support for installing `hostAttributes` and `listeners`.
      */
-    ready(): any;
+    ready(): void;
 
     /**
      * Overrides the default `Polymer.PropertyEffects` implementation to
      * add support for class initialization via the `_registered` callback.
      * This is called only when the first instance of the element is created.
      */
-    _initializeProperties(): any;
+    _initializeProperties(): void;
 
     /**
      * Provides an override implementation of `attributeChangedCallback`
@@ -60,31 +60,31 @@ declare namespace Polymer {
      * Provides an implementation of `connectedCallback`
      * which adds Polymer legacy API's `attached` method.
      */
-    connectedCallback(): any;
+    connectedCallback(): void;
 
     /**
      * Provides an implementation of `disconnectedCallback`
      * which adds Polymer legacy API's `detached` method.
      */
-    disconnectedCallback(): any;
+    disconnectedCallback(): void;
 
     /**
      * Legacy callback called during the `constructor`, for overriding
      * by the user.
      */
-    created(): any;
+    created(): void;
 
     /**
      * Legacy callback called during `connectedCallback`, for overriding
      * by the user.
      */
-    attached(): any;
+    attached(): void;
 
     /**
      * Legacy callback called during `disconnectedCallback`, for overriding
      * by the user.
      */
-    detached(): any;
+    detached(): void;
 
     /**
      * Legacy callback called during `attributeChangedChallback`, for overriding
@@ -94,7 +94,7 @@ declare namespace Polymer {
      * @param old Old value of attribute.
      * @param value Current value of attribute.
      */
-    attributeChanged(name: string, old: string|null, value: string|null): any;
+    attributeChanged(name: string, old: string|null, value: string|null): void;
 
     /**
      * Called automatically when an element is initializing.
@@ -102,7 +102,7 @@ declare namespace Polymer {
      * work. The implementation should ensure the work is performed
      * only once for the class.
      */
-    _registered(): any;
+    _registered(): void;
 
     /**
      * Ensures an element has required attributes. Called when the element
@@ -113,7 +113,7 @@ declare namespace Polymer {
      * to the element user and not done here; reasonable exceptions include
      * setting aria roles and focusability.
      */
-    _ensureAttributes(): any;
+    _ensureAttributes(): void;
 
     /**
      * Adds element event listeners. Called when the element
@@ -124,7 +124,7 @@ declare namespace Polymer {
      * these elements, consider adding listeners asynchronously so as not to
      * block render.
      */
-    _applyListeners(): any;
+    _applyListeners(): void;
 
     /**
      * Converts a typed JavaScript value to a string.
@@ -398,9 +398,13 @@ declare namespace Polymer {
     isLocalDescendant(node?: Element|null): boolean;
 
     /**
-     * NOTE: should now be handled by ShadyCss library.
+     * No-op for backwards compatibility. This should now be handled by
+     * ShadyCss library.
+     *
+     * @param container Unused
+     * @param shouldObserve Unused
      */
-    scopeSubtree(container: any, shouldObserve: any): any;
+    scopeSubtree(container: any, shouldObserve: any): void;
 
     /**
      * Returns the computed style value for the given property.
@@ -528,7 +532,7 @@ declare namespace Polymer {
      *    When unspecified, the state of the attribute will be reversed.
      * @param node Node to target.  Defaults to `this`.
      */
-    toggleAttribute(name: string, bool?: boolean, node?: Element|null): any;
+    toggleAttribute(name: string, bool?: boolean, node?: Element|null): void;
 
     /**
      * Toggles a CSS class on or off.
@@ -538,7 +542,7 @@ declare namespace Polymer {
      *    When unspecified, the state of the class will be reversed.
      * @param node Node to target.  Defaults to `this`.
      */
-    toggleClass(name: string, bool?: boolean, node?: Element|null): any;
+    toggleClass(name: string, bool?: boolean, node?: Element|null): void;
 
     /**
      * Cross-platform helper for setting an element's CSS `transform` property.
@@ -584,28 +588,28 @@ declare namespace Polymer {
      * @param level One of 'log', 'warn', 'error'
      * @param args Array of strings or objects to log
      */
-    _logger(level: string, args: any[]|null): any;
+    _logger(level: string, args: any[]|null): void;
 
     /**
      * Facades `console.log` as an override point.
      *
      * @param args Array of strings or objects to log
      */
-    _log(...args: any[]): any;
+    _log(...args: any[]): void;
 
     /**
      * Facades `console.warn` as an override point.
      *
      * @param args Array of strings or objects to log
      */
-    _warn(...args: any[]): any;
+    _warn(...args: any[]): void;
 
     /**
      * Facades `console.error` as an override point.
      *
      * @param args Array of strings or objects to log
      */
-    _error(...args: any[]): any;
+    _error(...args: any[]): void;
 
     /**
      * Formats a message using the element type an a method name.
diff --git a/types/lib/mixins/dir-mixin.d.ts b/types/lib/mixins/dir-mixin.d.ts
index 979a9cf1a9..066869c8fe 100644
--- a/types/lib/mixins/dir-mixin.d.ts
+++ b/types/lib/mixins/dir-mixin.d.ts
@@ -33,8 +33,8 @@ declare namespace Polymer {
   } & T
 
   interface DirMixin {
-    ready(): any;
-    connectedCallback(): any;
-    disconnectedCallback(): any;
+    ready(): void;
+    connectedCallback(): void;
+    disconnectedCallback(): void;
   }
 }
diff --git a/types/lib/mixins/element-mixin.d.ts b/types/lib/mixins/element-mixin.d.ts
index d6e4bb76ee..fe711889c4 100644
--- a/types/lib/mixins/element-mixin.d.ts
+++ b/types/lib/mixins/element-mixin.d.ts
@@ -90,7 +90,7 @@ declare namespace Polymer {
     /**
      * Stamps the element template.
      */
-    ready(): any;
+    ready(): void;
 
     /**
      * Overrides the default `Polymer.PropertyAccessors` to ensure class
@@ -100,7 +100,7 @@ declare namespace Polymer {
      * It also initializes any property defaults provided via `value` in
      * `properties` metadata.
      */
-    _initializeProperties(): any;
+    _initializeProperties(): void;
 
     /**
      * Implements `PropertyEffects`'s `_readyClients` call. Attaches
@@ -109,7 +109,7 @@ declare namespace Polymer {
      * client dom to be attached to the element prior to any observers
      * running.
      */
-    _readyClients(): any;
+    _readyClients(): void;
 
     /**
      * Provides a default implementation of the standard Custom Elements
@@ -119,7 +119,7 @@ declare namespace Polymer {
      * flushes any pending properties, and updates shimmed CSS properties
      * when using the ShadyCSS scoping/custom properties polyfill.
      */
-    connectedCallback(): any;
+    connectedCallback(): void;
 
     /**
      * Attaches an element's stamped dom to itself. By default,
diff --git a/types/lib/mixins/gesture-event-listeners.d.ts b/types/lib/mixins/gesture-event-listeners.d.ts
index c954cc8dd2..7d632f59b0 100644
--- a/types/lib/mixins/gesture-event-listeners.d.ts
+++ b/types/lib/mixins/gesture-event-listeners.d.ts
@@ -28,7 +28,23 @@ declare namespace Polymer {
   } & T
 
   interface GestureEventListeners {
-    _addEventListenerToNode(node: any, eventName: any, handler: any): any;
-    _removeEventListenerFromNode(node: any, eventName: any, handler: any): any;
+
+    /**
+     * Add the event listener to the node if it is a gestures event.
+     *
+     * @param node Node to add event listener to
+     * @param eventName Name of event
+     * @param handler Listener function to add
+     */
+    _addEventListenerToNode(node: Node, eventName: string, handler: Function): void;
+
+    /**
+     * Remove the event listener to the node if it is a gestures event.
+     *
+     * @param node Node to remove event listener from
+     * @param eventName Name of event
+     * @param handler Listener function to remove
+     */
+    _removeEventListenerFromNode(node: Node, eventName: string, handler: Function): void;
   }
 }
diff --git a/types/lib/mixins/properties-changed.d.ts b/types/lib/mixins/properties-changed.d.ts
index 4dabca1f14..22bf9ffceb 100644
--- a/types/lib/mixins/properties-changed.d.ts
+++ b/types/lib/mixins/properties-changed.d.ts
@@ -50,7 +50,7 @@ declare namespace Polymer {
      * @param readOnly When true, no setter is created; the
      *   protected `_setProperty` function must be used to set the property
      */
-    _createPropertyAccessor(property: string, readOnly?: boolean): any;
+    _createPropertyAccessor(property: string, readOnly?: boolean): void;
 
     /**
      * Defines a property accessor for the given property.
@@ -58,7 +58,7 @@ declare namespace Polymer {
      * @param property Name of the property
      * @param readOnly When true, no setter is created
      */
-    _definePropertyAccessor(property: string, readOnly?: boolean): any;
+    _definePropertyAccessor(property: string, readOnly?: boolean): void;
 
     /**
      * Lifecycle callback called when properties are enabled via
@@ -71,7 +71,7 @@ declare namespace Polymer {
      * bindings.  `super.ready()` must be called to ensure the data system
      * becomes enabled.
      */
-    ready(): any;
+    ready(): void;
 
     /**
      * Initializes the local storage for property accessors.
@@ -79,7 +79,7 @@ declare namespace Polymer {
      * Provided as an override point for performing any setup work prior
      * to initializing the property accessor system.
      */
-    _initializeProperties(): any;
+    _initializeProperties(): void;
 
     /**
      * Called at ready time with bag of instance properties that overwrote
@@ -92,7 +92,7 @@ declare namespace Polymer {
      * @param props Bag of property values that were overwritten
      *   when creating property accessors.
      */
-    _initializeInstanceProperties(props: object|null): any;
+    _initializeInstanceProperties(props: object|null): void;
 
     /**
      * Updates the local storage for a property (via `_setPendingProperty`)
@@ -101,7 +101,7 @@ declare namespace Polymer {
      * @param property Name of the property
      * @param value Value to set
      */
-    _setProperty(property: string, value: any): any;
+    _setProperty(property: string, value: any): void;
 
     /**
      * Returns the value for the given property.
@@ -128,7 +128,7 @@ declare namespace Polymer {
      * Marks the properties as invalid, and enqueues an async
      * `_propertiesChanged` callback.
      */
-    _invalidateProperties(): any;
+    _invalidateProperties(): void;
 
     /**
      * Call to enable property accessor processing. Before this method is
@@ -138,7 +138,7 @@ declare namespace Polymer {
      * It is safe to call this method multiple times as it only turns on
      * property accessors once.
      */
-    _enableProperties(): any;
+    _enableProperties(): void;
 
     /**
      * Calls the `_propertiesChanged` callback with the current set of
@@ -146,7 +146,7 @@ declare namespace Polymer {
      * set), and resets the pending set of changes. Generally, this method
      * should not be called in user code.
      */
-    _flushProperties(): any;
+    _flushProperties(): void;
 
     /**
      * Callback called when any properties with accessors created via
@@ -158,7 +158,7 @@ declare namespace Polymer {
      * @param oldProps Bag of previous values for each property
      *   in `changedProps`
      */
-    _propertiesChanged(currentProps: object, changedProps: object, oldProps: object): any;
+    _propertiesChanged(currentProps: object, changedProps: object, oldProps: object): void;
 
     /**
      * Method called to determine whether a property value should be
@@ -188,7 +188,7 @@ declare namespace Polymer {
      * @param old Old attribute value
      * @param value New attribute value
      */
-    attributeChangedCallback(name: string, old: string|null, value: string|null): any;
+    attributeChangedCallback(name: string, old: string|null, value: string|null): void;
 
     /**
      * Deserializes an attribute to its associated property.
@@ -201,7 +201,7 @@ declare namespace Polymer {
      * @param type type to deserialize to, defaults to the value
      * returned from `typeForProperty`
      */
-    _attributeToProperty(attribute: string, value: string|null, type?: any): any;
+    _attributeToProperty(attribute: string, value: string|null, type?: any): void;
 
     /**
      * Serializes a property to its associated attribute.
@@ -210,7 +210,7 @@ declare namespace Polymer {
      * @param attribute Attribute name to reflect to.
      * @param value Property value to refect.
      */
-    _propertyToAttribute(property: string, attribute?: string, value?: any): any;
+    _propertyToAttribute(property: string, attribute?: string, value?: any): void;
 
     /**
      * Sets a typed value to an HTML attribute on a node.
@@ -224,7 +224,7 @@ declare namespace Polymer {
      * @param value Value to serialize.
      * @param attribute Attribute name to serialize to.
      */
-    _valueToNodeAttribute(node: Element|null, value: any, attribute: string): any;
+    _valueToNodeAttribute(node: Element|null, value: any, attribute: string): void;
 
     /**
      * Converts a typed JavaScript value to a string.
diff --git a/types/lib/mixins/properties-mixin.d.ts b/types/lib/mixins/properties-mixin.d.ts
index d31e89cd3b..2149fa599f 100644
--- a/types/lib/mixins/properties-mixin.d.ts
+++ b/types/lib/mixins/properties-mixin.d.ts
@@ -35,18 +35,18 @@ declare namespace Polymer {
      * Overrides `PropertiesChanged` method and adds a call to
      * `finalize` which lazily configures the element's property accessors.
      */
-    _initializeProperties(): any;
+    _initializeProperties(): void;
 
     /**
      * Called when the element is added to a document.
      * Calls `_enableProperties` to turn on property system from
      * `PropertiesChanged`.
      */
-    connectedCallback(): any;
+    connectedCallback(): void;
 
     /**
      * Called when the element is removed from a document
      */
-    disconnectedCallback(): any;
+    disconnectedCallback(): void;
   }
 }
diff --git a/types/lib/mixins/property-effects.d.ts b/types/lib/mixins/property-effects.d.ts
index 191ae6fb5d..1825a1254e 100644
--- a/types/lib/mixins/property-effects.d.ts
+++ b/types/lib/mixins/property-effects.d.ts
@@ -77,8 +77,8 @@ declare namespace Polymer {
      * Also calls `_flushClients` callback to ensure client dom is enabled
      * that was not enabled as a result of flushing properties.
      */
-    ready(): any;
-    _initializeProperties(): any;
+    ready(): void;
+    _initializeProperties(): void;
 
     /**
      * Overrides `Polymer.PropertyAccessors` implementation to avoid setting
@@ -86,13 +86,16 @@ declare namespace Polymer {
      *
      * @param props Properties to initialize on the instance
      */
-    _initializeInstanceProperties(props: object|null): any;
+    _initializeInstanceProperties(props: object|null): void;
 
     /**
      * Overrides base implementation to ensure all accessors set `shouldNotify`
      * to true, for per-property notification tracking.
+     *
+     * @param property Name of the property
+     * @param value Value to set
      */
-    _setProperty(property: any, value: any): any;
+    _setProperty(property: string, value: any): void;
 
     /**
      * Overrides the `PropertiesChanged` implementation to introduce special
@@ -136,20 +139,26 @@ declare namespace Polymer {
      * manually flushed), the function no-ops; otherwise flushes
      * `_propertiesChanged` synchronously.
      */
-    _invalidateProperties(): any;
+    _invalidateProperties(): void;
 
     /**
      * Overrides superclass implementation.
      */
-    _flushProperties(): any;
+    _flushProperties(): void;
 
     /**
      * Implements `PropertyAccessors`'s properties changed callback.
      *
      * Runs each class of effects for the batch of changed properties in
      * a specific order (compute, propagate, reflect, observe, notify).
+     *
+     * @param currentProps Bag of all current accessor values
+     * @param changedProps Bag of properties changed since the last
+     *   call to `_propertiesChanged`
+     * @param oldProps Bag of previous values for each property
+     *   in `changedProps`
      */
-    _propertiesChanged(currentProps: any, changedProps: any, oldProps: any): any;
+    _propertiesChanged(currentProps: object, changedProps: object, oldProps: object): void;
 
     /**
      * Overrides `Polymer.PropertyAccessors` implementation to provide a
@@ -158,7 +167,7 @@ declare namespace Polymer {
      *
      * @param props Properties to initialize on the prototype
      */
-    _initializeProtoProperties(props: object|null): any;
+    _initializeProtoProperties(props: object|null): void;
 
     /**
      * Equivalent to static `addPropertyEffect` API but can be called on
diff --git a/types/lib/mixins/template-stamp.d.ts b/types/lib/mixins/template-stamp.d.ts
index bfbaa9af16..c417ea9a88 100644
--- a/types/lib/mixins/template-stamp.d.ts
+++ b/types/lib/mixins/template-stamp.d.ts
@@ -65,7 +65,7 @@ declare namespace Polymer {
      *   to `node`)
      * @returns Generated handler function
      */
-    _addMethodEventListenerToNode(node: Node|null, eventName: string, methodName: string, context?: any): Function|null;
+    _addMethodEventListenerToNode(node: Node, eventName: string, methodName: string, context?: any): Function;
 
     /**
      * Override point for adding custom or simulated event handling.
@@ -74,7 +74,7 @@ declare namespace Polymer {
      * @param eventName Name of event
      * @param handler Listener function to add
      */
-    _addEventListenerToNode(node: Node|null, eventName: string, handler: Function|null): void;
+    _addEventListenerToNode(node: Node, eventName: string, handler: Function): void;
 
     /**
      * Override point for adding custom or simulated event handling.
diff --git a/types/lib/utils/flattened-nodes-observer.d.ts b/types/lib/utils/flattened-nodes-observer.d.ts
index e6f5d2ed25..556ef57167 100644
--- a/types/lib/utils/flattened-nodes-observer.d.ts
+++ b/types/lib/utils/flattened-nodes-observer.d.ts
@@ -68,9 +68,6 @@ declare namespace Polymer {
      * the observer.
      */
     disconnect(): void;
-    _schedule(): any;
-    _processMutations(mutations: any): any;
-    _processSlotMutations(mutations: any): any;
 
     /**
      * Flushes the observer causing any pending changes to be immediately
@@ -81,7 +78,5 @@ declare namespace Polymer {
      * callback to run.
      */
     flush(): boolean;
-    _listenSlots(nodeList: any): any;
-    _unlistenSlots(nodeList: any): any;
   }
 }
diff --git a/types/lib/utils/templatize.d.ts b/types/lib/utils/templatize.d.ts
index dc866ad9cf..b08485e824 100644
--- a/types/lib/utils/templatize.d.ts
+++ b/types/lib/utils/templatize.d.ts
@@ -15,14 +15,26 @@
 declare class TemplateInstanceBase extends
   Polymer.PropertyEffects(
   Polymer.Element) {
-  _addEventListenerToNode(node: any, eventName: any, handler: any): any;
+
+  /**
+   * Override point for adding custom or simulated event handling.
+   *
+   * @param node Node to add event listener to
+   * @param eventName Name of event
+   * @param handler Listener function to add
+   */
+  _addEventListenerToNode(node: Node, eventName: string, handler: Function): void;
 
   /**
    * Overrides default property-effects implementation to intercept
    * textContent bindings while children are "hidden" and cache in
    * private storage for later retrieval.
+   *
+   * @param node The node to set a property on
+   * @param prop The property to set
+   * @param value The value to set
    */
-  _setUnmanagedPropertyToNode(node: any, prop: any, value: any): any;
+  _setUnmanagedPropertyToNode(node: Node|null, prop: string, value: any): void;
 
   /**
    * Forwards a host property to this instance.  This method should be