MD History: Add spinners when new data is loading or searching

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.
 
 /**
  * @constructor
  * @implements {SearchFieldDelegate}
  * @param {!HistoryToolbarElement} toolbar This history-toolbar.
  */
 function ToolbarSearchFieldDelegate(toolbar) {
@@ skipping 23 matching lines @@
       type: Boolean,
       value: false,
       reflectToAttribute: true
     },
 
     // The most recent term entered in the search field. Updated incrementally
     // as the user types.
     searchTerm: {
       type: String,
       value: ''
+    },
+
+    // True if it's searching at the backend.
+    searching_: {
+      type: Boolean,
+      value: false
     }
   },
 
   /**
    * Changes the toolbar background color depending on whether any history items
    * are currently selected.
    * @private
    */
   changeToolbarView_: function() {
     this.itemsSelected_ = this.count > 0;
   },
 
   /**
    * When changing the search term externally, update the search field to
    * reflect the new search term.
    * @param {string} search
    */
   setSearchTerm: function(search) {
     if (this.searchTerm == search)
       return;
     this.searchTerm = search;
     var searchField = /** @type {SearchField} */(this.$['search-input']);
     searchField.showAndFocus().then(function(showing) {
       if (showing) searchField.setValue(search);
     });
   },
 
   /**
+  * Mark the toolbar as currently searching term from the back-end.

[tsergeant, 2016/04/15 05:14:50]

You can either replace these two functions with a single one:
  setSearching(value)

Or make the `searching_` property public and have history.js modify it directly:

$('toolbar').searching = true;

^ This second one has the advantage of probably not needing waitForUpgrade
anymore.

[lshang, 2016/04/18 00:29:00]

Done.

+  */
+  setSearching: function() {
+    this.searching_ = true;
+  },
+
+  /**
+  * Set searching as finished so that searching spinner is hidden.
+  */
+  searchingFinished: function() {
+    this.searching_ = false;
+  },
+
+
+  /**
    * If the search term has changed reload for the new search.
    */
   onSearch: function(searchTerm) {
     if (searchTerm != this.searchTerm) {
       this.searchTerm = searchTerm;
       this.fire('search-changed', {search: searchTerm});
     }
   },
 
   attached: function() {
@@ skipping 23 matching lines @@
    * @private
    */
   deletingAllowed_: function() {
     return loadTimeData.getBoolean('allowDeletingHistory');
   },
 
   numberOfItemsSelected_: function(count) {
     return count > 0 ? loadTimeData.getStringF('itemsSelected', count) : '';
   }
 });