MD History: Add a keyboard shortcut to open grouped mode

chrome/browser/resources/md_history/app.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.
 
 cr.define('md_history', function() {
   var lazyLoadPromise = null;
   function ensureLazyLoaded() {
     if (!lazyLoadPromise) {
       lazyLoadPromise = new Promise(function(resolve, reject) {
         Polymer.Base.importHref(
@@ skipping 220 matching lines @@
   focusToolbarSearchField: function() { this.$.toolbar.showSearchField(); },
 
   /**
    * @param {Event} e
    * @private
    */
   onCanExecute_: function(e) {
     e = /** @type {cr.ui.CanExecuteEvent} */(e);
     switch (e.command.id) {
       case 'find-command':
+      case 'toggle-grouped':
         e.canExecute = true;
         break;
       case 'slash-command':
         e.canExecute = !this.$.toolbar.searchField.isSearchFocused();
         break;
       case 'delete-command':
         e.canExecute = this.$.toolbar.count > 0;
         break;
     }
   },
 
   /**
    * @param {Event} e
    * @private
    */
   onCommand_: function(e) {
     if (e.command.id == 'find-command' || e.command.id == 'slash-command')
       this.focusToolbarSearchField();
     if (e.command.id == 'delete-command')
       this.deleteSelected();
+    if (e.command.id == 'toggle-grouped')
+      this.grouped_ = !this.grouped_;
   },
 
   /**
    * @param {!Array<!ForeignSession>} sessionList Array of objects describing
    *     the sessions from other devices.
    * @param {boolean} isTabSyncEnabled Is tab sync enabled for this profile?
    */
   setForeignSessions: function(sessionList, isTabSyncEnabled) {
     if (!isTabSyncEnabled) {
       var syncedDeviceManagerElem =
@@ skipping 123 matching lines @@
             break;
         }
         break;
     }
 
     md_history.BrowserService.getInstance().recordHistogram(
       'History.HistoryPageView', histogramValue, HistoryPageViewHistogram.END
     );
   },
 });