MD History: add shortcuts for search

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.
     count: {
       type: Number,
@@ skipping 78 matching lines @@
   },
 
   onClearSelectionTap_: function() {
     this.fire('unselect-all');
   },
 
   onDeleteTap_: function() {
     this.fire('delete-selected');
   },
 
+  showSearchField: function() {
+    /** @type {!CrToolbarElement} */(this.$['main-toolbar'])
+        .getSearchField()
+        .showAndFocus();
+  },
+
   /**
    * If the user is a supervised user the delete button is not shown.
    * @private
    */
   deletingAllowed_: function() {
     return loadTimeData.getBoolean('allowDeletingHistory');
   },
 
   numberOfItemsSelected_: function(count) {
     return count > 0 ? loadTimeData.getStringF('itemsSelected', count) : '';
   },
 
   getHistoryInterval_: function(queryStartTime, queryEndTime) {
     // TODO(calamity): Fix the format of these dates.
     return loadTimeData.getStringF(
       'historyInterval', queryStartTime, queryEndTime);
   }
 });