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-light-extracted.js

 (function() {
       'use strict';
 
       Polymer({
         is: 'paper-dropdown-menu-light',
 
         behaviors: [
           Polymer.IronButtonState,
           Polymer.IronControlState,
           Polymer.PaperRippleBehavior,
@@ skipping 56 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 185 matching lines @@
 
         _valueChanged: function() {
           // Only update if it's actually different.
           if (this.$.input && this.$.input.textContent !== this.value) {
             this.$.input.textContent = this.value;
           }
           this._setHasContent(!!this.value);
         },
       });
     })();