MD History: Add confirmation dialog when deleting items from the toolbar

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 65 matching lines @@
       queryState.searchTerm, queryState.groupedOffset, queryState.range,
       lastVisitTime, maxResults
     ]);
   },
 
   unselectAllItems: function(count) {
     /** @type {HistoryListElement} */ (this.$['infinite-list'])
         .unselectAllItems(count);
   },
 
-  deleteSelected: function() {
-    /** @type {HistoryListElement} */ (this.$['infinite-list'])
-        .deleteSelected();
+  /**
+   * Delete all the currently selected history items. Will prompt the user with
+   * a dialog to confirm that the deletion should be performed.
+   */
+  deleteSelectedWithPrompt: function() {
+    if (!loadTimeData.getBoolean('allowDeletingHistory'))
+      return;
+
+    this.$.dialog.open();
   },
 
   /**
    * @param {string} searchTerm
    * @private
    */
   searchTermChanged_: function(searchTerm) { this.queryHistory(false); },
 
   /**
    * @param {HistoryRange} range
@@ skipping 25 matching lines @@
       // Sets the default values for these fields to prevent undefined types.
       results[i].selected = false;
       results[i].readableTimestamp =
           info.term == '' ? results[i].dateTimeOfDay : results[i].dateShort;
 
       if (results[i].dateRelativeDay != currentDate) {
         currentDate = results[i].dateRelativeDay;
       }
     }
   },
+
+  /** @private */
+  onDialogConfirmTap_: function() {
+    this.$['infinite-list'].deleteSelected();
+    this.$.dialog.close();
+  },
+
+  /** @private */
+  onDialogCancelTap_: function() {
+    this.$.dialog.close();
+  }
 });