ash: Use system tray mojo interface to show system update tray icon

ash/common/system/tray/system_tray.cc

 // Copyright (c) 2012 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.
 
 #include "ash/common/system/tray/system_tray.h"
 
 #include <algorithm>
 #include <map>
 #include <vector>
 
@@ skipping 804 matching lines @@
 }
 
 TraySystemInfo* SystemTray::GetTraySystemInfoForTesting() const {
   return tray_system_info_;
 }
 
 TrayTiles* SystemTray::GetTrayTilesForTesting() const {
   return tray_tiles_;
 }
 
-TrayUpdate* SystemTray::GetTrayUpdateForTesting() const {
-  return tray_update_;
-}
-
 void SystemTray::CloseBubble(const ui::KeyEvent& key_event) {
   CloseSystemBubble();
 }
 
 void SystemTray::ActivateAndStartNavigation(const ui::KeyEvent& key_event) {
   if (!system_bubble_)
     return;
   activating_ = true;
   ActivateBubble();
   activating_ = false;
@@ skipping 76 matching lines @@
           .work_area()
           .height();
   if (work_area_height > 0) {
     UMA_HISTOGRAM_CUSTOM_COUNTS(
         "Ash.SystemMenu.PercentageOfWorkAreaHeightCoveredByMenu",
         100 * bubble_view->height() / work_area_height, 1, 300, 100);
   }
 }
 
 }  // namespace ash