feat(layout): add flex fixed attribute to prevent shrinking

Fixes angular#6067

Author: devversion

src/core/services/layout/layout.js

@@ -6,7 +6,7 @@
   var SUFFIXES = /(-gt)?-(sm|md|lg)/g;
   var WHITESPACE = /\s+/g;
 
-  var FLEX_OPTIONS = ['grow', 'initial', 'auto', 'none'];
+  var FLEX_OPTIONS = ['grow', 'initial', 'auto', 'none', 'fixed'];
   var LAYOUT_OPTIONS = ['row', 'column'];
   var ALIGNMENT_MAIN_AXIS= [ "", "start", "center", "end", "stretch", "space-around", "space-between" ];
   var ALIGNMENT_CROSS_AXIS= [ "", "start", "center", "end", "stretch" ];

src/core/services/layout/layout.scss

@@ -130,6 +130,7 @@
   .#{$flexName}-initial     { flex: 0 1 auto;  box-sizing: border-box; }
   .#{$flexName}-auto        { flex: 1 1 auto;  box-sizing: border-box; }
   .#{$flexName}-none        { flex: 0 0 auto;  box-sizing: border-box; }
+  .#{$flexName}-fixed       { flex: 1 0 auto;  box-sizing: border-box; }
 
   // (1-20) * 5 = 0-100%
   @for $i from 0 through 20 {