chromeos: Make system tray audio item observe CrasAudioHandler directly

ash/common/wm_root_window_controller.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_ROOT_WINDOW_CONTROLLER_H_
 #define ASH_COMMON_WM_ROOT_WINDOW_CONTROLLER_H_
 
 #include "ash/ash_export.h"
 #include "ash/common/wm/workspace/workspace_types.h"
 #include "base/macros.h"
@@ skipping 13 matching lines @@
 class MenuRunner;
 }
 
 namespace ash {
 
 class AlwaysOnTopController;
 class AnimatingWallpaperWidgetController;
 class DockedWindowLayoutManager;
 class PanelLayoutManager;
 class SystemModalContainerLayoutManager;
+class SystemTray;
 class WallpaperWidgetController;
 class WmShelf;
 class WmShell;
 class WmWindow;
 class WorkspaceController;
 
 enum class LoginStatus;
 
 namespace wm {
 class RootWindowLayoutManager;
@@ skipping 52 matching lines @@
 
   virtual WmShelf* GetShelf() = 0;
 
   // Creates the shelf for this root window and notifies observers.
   void CreateShelf();
 
   // Show shelf view if it was created hidden (before session has started).
   // TODO(jamescook): Eliminate this and handle show via Shelf.
   void ShowShelf();
 
+  // Returns the system tray controller. May be null for external displays.
+  SystemTray* GetSystemTray();
+
   // Returns the window associated with this WmRootWindowController.
   virtual WmWindow* GetWindow() = 0;
 
   // Gets the WmWindow whose shell window id is |container_id|.
   WmWindow* GetContainer(int container_id);
   const WmWindow* GetContainer(int container_id) const;
 
   // Configures |init_params| prior to initializing |widget|.
   // |shell_container_id| is the id of the container to parent |widget| to.
   virtual void ConfigureWidgetInitParamsForContainer(
@@ skipping 69 matching lines @@
   std::unique_ptr<ui::MenuModel> menu_model_;
   std::unique_ptr<views::MenuModelAdapter> menu_model_adapter_;
   std::unique_ptr<views::MenuRunner> menu_runner_;
 
   DISALLOW_COPY_AND_ASSIGN(WmRootWindowController);
 };
 
 }  // namespace ash
 
 #endif  // ASH_COMMON_WM_ROOT_WINDOW_CONTROLLER_H_