Roll Polymer to 1.3.1

third_party/polymer/v1_0/components-chromium/paper-header-panel/paper-header-panel-extracted.js

 (function() {
       'use strict';
 
       var SHADOW_WHEN_SCROLLING = 1;
       var SHADOW_ALWAYS = 2;
       var MODE_CONFIGS = {
         outerScroll: {
           'scroll': true
         },
 
@@ skipping 85 matching lines @@
             value: 'tall'
           },
 
           /**
            * If true, the scroller is at the top
            */
           atTop: {
             type: Boolean,
             value: true,
             notify: true,
-            readOnly: true
+            readOnly: true,
+            reflectToAttribute: true
           }
         },
 
         observers: [
           '_computeDropShadowHidden(atTop, mode, shadow)'
         ],
 
         ready: function() {
           this.scrollHandler = this._scroll.bind(this);
         },
@@ skipping 111 matching lines @@
           this._keepScrollingState();
           this.fire('content-scroll', {target: this.scroller}, {bubbles: false});
         },
 
         _getScrollerForMode: function(mode) {
           return MODE_CONFIGS.outerScroll[mode] ?
               this : this.$.mainContainer;
         }
       });
     })();