MD History: Use iron-a11y-announcer to announce search result messages

chrome/browser/resources/md_history/list_container.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.
 
 Polymer({
   is: 'history-list-container',
 
   properties: {
     // The path of the currently selected page.
     selectedPage_: String,
@@ skipping 24 matching lines @@
   /**
    * @param {HistoryQuery} info An object containing information about the
    *    query.
    * @param {!Array<HistoryEntry>} results A list of results.
    */
   historyResult: function(info, results) {
     this.initializeResults_(info, results);
     this.closeMenu_();
 
     if (info.term && !this.queryState.incremental) {
-      announceAccessibleMessage(
-          md_history.HistoryItem.searchResultsTitle(results.length, info.term));
+      Polymer.IronA11yAnnouncer.requestAvailability();
+      this.fire('iron-announce', {
+        text:
+            md_history.HistoryItem.searchResultsTitle(results.length, info.term)
+      });
     }
 
     if (this.selectedPage_ == 'grouped-list') {
       this.$$('#grouped-list').historyData = results;
       return;
     }
 
     var list = /** @type {HistoryListElement} */(this.$['infinite-list']);
     list.addNewResults(results, this.queryState.incremental);
     if (info.finished)
@@ skipping 210 matching lines @@
         }.bind(this));
     menu.closeMenu();
   },
 
   /**
    * @return {HTMLElement}
    * @private
    */
   getSelectedList_: function() { return this.$.content.selectedItem; },
 });