Roll Polymer from 1.5.0 -> 1.6.0 to pick up native CSS custom props

third_party/polymer/v1_0/components-chromium/paper-dropdown-menu/paper-dropdown-menu-extracted.js

 (function() {
       'use strict';
 
       Polymer({
         is: 'paper-dropdown-menu',
 
         behaviors: [
           Polymer.IronButtonState,
           Polymer.IronControlState,
           Polymer.IronFormElementBehavior,
@@ skipping 61 matching lines @@
            * True if the dropdown is open. Otherwise, false.
            */
           opened: {
             type: Boolean,
             notify: true,
             value: false,
             observer: '_openedChanged'
           },
 
           /**
+           * By default, the dropdown will constrain scrolling on the page
+           * to itself when opened.
+           * Set to true in order to prevent scroll from being constrained
+           * to the dropdown when it opens.
+           */
+          allowOutsideScroll: {
+            type: Boolean,
+            value: false
+          },
+
+          /**
            * Set to true to disable the floating label. Bind this to the
            * `<paper-input-container>`'s `noLabelFloat` property.
            */
           noLabelFloat: {
               type: Boolean,
               value: false,
               reflectToAttribute: true
           },
 
           /**
@@ skipping 117 matching lines @@
          * Compute the label for the dropdown given a selected item.
          *
          * @param {Element} selectedItem A selected Element item, with an
          * optional `label` property.
          */
         _selectedItemChanged: function(selectedItem) {
           var value = '';
           if (!selectedItem) {
             value = '';
           } else {
-            value = selectedItem.label || selectedItem.textContent.trim();
+            value = selectedItem.label || selectedItem.getAttribute('label') || selectedItem.textContent.trim();
           }
 
           this._setValue(value);
           this._setSelectedItemLabel(value);
         },
 
         /**
          * Compute the vertical offset of the menu based on the value of
          * `noLabelFloat`.
          *
@@ skipping 21 matching lines @@
 
         _openedChanged: function() {
           var openState = this.opened ? 'true' : 'false';
           var e = this.contentElement;
           if (e) {
             e.setAttribute('aria-expanded', openState);
           }
         }
       });
     })();