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

ash/common/system/tray/system_tray.h

 // 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.
 
 #ifndef ASH_COMMON_SYSTEM_TRAY_SYSTEM_TRAY_H_
 #define ASH_COMMON_SYSTEM_TRAY_SYSTEM_TRAY_H_
 
 #include <map>
 #include <memory>
 #include <vector>
@@ skipping 29 matching lines @@
   BUBBLE_CREATE_NEW,    // Closes any existing bubble and creates a new one.
   BUBBLE_USE_EXISTING,  // Uses any existing bubble, or creates a new one.
 };
 
 class ASH_EXPORT SystemTray : public TrayBackgroundView,
                               public views::TrayBubbleView::Delegate {
  public:
   explicit SystemTray(WmShelf* wm_shelf);
   ~SystemTray() override;
 
+  TrayUpdate* tray_update() { return tray_update_; }
+
   // Calls TrayBackgroundView::Initialize(), creates the tray items, and
   // adds them to SystemTrayNotifier.
   void InitializeTrayItems(SystemTrayDelegate* delegate,
                            WebNotificationTray* web_notification_tray);
 
   // Resets internal pointers. This has to be called before deletion.
   void Shutdown();
 
   // Adds a new item in the tray. Takes ownership.
   void AddTrayItem(SystemTrayItem* item);
@@ skipping 101 matching lines @@
   }
 
   // Get the tray item view (or NULL) for a given |tray_item| in a unit test.
   views::View* GetTrayItemViewForTest(SystemTrayItem* tray_item);
 
   TrayCast* GetTrayCastForTesting() const;
   TrayDate* GetTrayDateForTesting() const;
   TrayNetwork* GetTrayNetworkForTesting() const;
   TraySystemInfo* GetTraySystemInfoForTesting() const;
   TrayTiles* GetTrayTilesForTesting() const;
-  TrayUpdate* GetTrayUpdateForTesting() const;
 
   // Activates the system tray bubble.
   void ActivateBubble();
 
  private:
   class ActivationObserver;
 
   // Closes the bubble. Used to bind as a KeyEventWatcher::KeyEventCallback.
   void CloseBubble(const ui::KeyEvent& key_event);
 
@@ skipping 102 matching lines @@
   std::unique_ptr<KeyEventWatcher> key_event_watcher_;
 
   std::unique_ptr<ActivationObserver> activation_observer_;
 
   DISALLOW_COPY_AND_ASSIGN(SystemTray);
 };
 
 }  // namespace ash
 
 #endif  // ASH_COMMON_SYSTEM_TRAY_SYSTEM_TRAY_H_