Mixin for #sizedImgDiv added

iron-image.html

@@ -60,6 +60,7 @@
 
 Custom property | Description | Default
 ----------------|-------------|----------
+`--iron-image-sized-img` | Mixin applied to #sizedImageDiv | `{}`
 `--iron-image-placeholder` | Mixin applied to #placeholder | `{}`
 `--iron-image-width` | Sets the width of the wrapped image | `auto`
 `--iron-image-height` | Sets the height of the wrapped image | `auto`
@@ -82,6 +83,8 @@
         @apply(--layout-fit);
 
         display: none;
+
+        @apply(--iron-image-sized-img);
       }
 
       #img {