MD History: hide tooltip promo when drawer is swiped open

chrome/browser/resources/md_history/history_toolbar.js

 // Copyright 2015 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 Polymer({
   is: 'history-toolbar',
   properties: {
     // Number of history items currently selected.
     // TODO(calamity): bind this to
     // listContainer.selectedItem.selectedPaths.length.
@@ skipping 49 matching lines @@
     },
 
     // The start time of the query range.
     queryStartTime: String,
 
     // The end time of the query range.
     queryEndTime: String,
 
     // Whether to show the menu promo (a tooltip that points at the menu button
     // in narrow mode).
-    showMenuPromo_: {
+    showMenuPromo: {
       type: Boolean,
-      value: function() {
-        return loadTimeData.getBoolean('showMenuPromo');
-      },
+      notify: true,
     },
   },
 
   /** @return {CrToolbarSearchFieldElement} */
   get searchField() {
     return /** @type {CrToolbarElement} */ (this.$['main-toolbar'])
         .getSearchField();
   },
 
   showSearchField: function() {
@@ skipping 67 matching lines @@
     // TODO(calamity): Fix the format of these dates.
     return loadTimeData.getStringF(
       'historyInterval', queryStartTime, queryEndTime);
   },
 
   /** @private */
   hasDrawerChanged_: function() {
     this.updateStyles();
   },
 });