mash: Introduce WmSystemTrayNotifier for //ash/common

ash/common/wm_shell.h

 // 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.
 
 #ifndef ASH_COMMON_WM_SHELL_H_
 #define ASH_COMMON_WM_SHELL_H_
 
 #include <stdint.h>
 
 #include <memory>
 #include <vector>
 
 #include "ash/ash_export.h"
 
 namespace gfx {
 class Rect;
 }
 
 namespace ash {
 
 class AccessibilityDelegate;
 class MruWindowTracker;
 class SessionStateDelegate;
 class ShellObserver;
 class SystemTrayDelegate;
 class WindowResizer;
 class WmActivationObserver;
 class WmDisplayObserver;
+class WmSystemTrayNotifier;
 class WmWindow;
 
 namespace wm {
 
 class WindowState;
 
 enum class WmUserMetricsAction;
 }
 
 // Similar to ash::Shell. Eventually the two will be merged.
 class ASH_EXPORT WmShell {
  public:
   // This is necessary for a handful of places that is difficult to plumb
   // through context.
   static void Set(WmShell* instance);
   static WmShell* Get();
   static bool HasInstance() { return instance_ != nullptr; }
 
+  WmSystemTrayNotifier* system_tray_notifier() {
+    return system_tray_notifier_.get();
+  }
+
   SystemTrayDelegate* system_tray_delegate() {
     return system_tray_delegate_.get();
   }
 
   virtual MruWindowTracker* GetMruWindowTracker() = 0;
 
   // Creates a new window used as a container of other windows. No painting is
   // done to the created window.
   virtual WmWindow* NewContainerWindow() = 0;
 
@@ skipping 68 matching lines @@
 
   // If |delegate| is not null, sets and initializes the delegate. If |delegate|
   // is null, shuts down and destroys the delegate.
   void SetSystemTrayDelegate(std::unique_ptr<SystemTrayDelegate> delegate);
 
  private:
   friend class Shell;
 
   static WmShell* instance_;
 
+  std::unique_ptr<WmSystemTrayNotifier> system_tray_notifier_;
   std::unique_ptr<SystemTrayDelegate> system_tray_delegate_;
 };
 
 }  // namespace ash
 
 #endif  // ASH_COMMON_WM_SHELL_H_