[MD History] Add UMA stats for switching views and the CBD button.

chrome/browser/resources/md_history/side_bar.js

 // Copyright 2016 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.
 
-// Histogram buckets for UMA tracking of menu usage.
-/** @const */ var MENU_HISTOGRAM = {
-  HISTORY: 0,
-  SYNCED_TABS: 1,
-  END: 2,  // Should always be last.
-};
-
 Polymer({
   is: 'history-side-bar',
 
   properties: {
     selectedPage:
-        {type: String, notify: true, observer: 'selectedPageChanged_'},
+        {type: String, notify: true},
 
     route: Object,
 
     showFooter: Boolean,
 
     // If true, the sidebar is contained within an app-drawer.
     drawer: {type: Boolean, reflectToAttribute: true},
   },
 
   /**
    * @param {Event} e
    * @private
    */
   onSelectorActivate_: function(e) {
     this.fire('history-close-drawer');
   },
 
-  selectedPageChanged_: function(value, oldValue) {
-    if (!this.$.menu.selectedItem)
-      return;
-
-    var histogramValue = MENU_HISTOGRAM.END;
-    switch(this.$.menu.selectedItem.getAttribute('path')) {
-      case 'history':
-        histogramValue = MENU_HISTOGRAM.HISTORY;
-        break;
-      case 'syncedTabs':
-        histogramValue = MENU_HISTOGRAM.SYNCED_TABS;
-        break;
-    }
-    md_history.BrowserService.getInstance().recordHistogram(
-        ['History.SidebarMenuSelected', histogramValue, MENU_HISTOGRAM.END]);
-  },
-
   /**
    * Relocates the user to the clear browsing data section of the settings page.
    * @param {Event} e
    * @private
    */
   onClearBrowsingDataTap_: function(e) {
     md_history.BrowserService.getInstance().recordAction(
         ['HistoryPage_InitClearBrowsingData']);
     md_history.BrowserService.getInstance().openClearBrowsingData();
     e.preventDefault();
   },
 
   /**
    * @param {Object} route
    * @private
    */
   getQueryString_: function(route) { return window.location.search; }
 });