WIP: Eliminate event.target() usage from TrayEventFilter

mash/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 MASH_WM_ROOT_WINDOW_CONTROLLER_H_
 #define MASH_WM_ROOT_WINDOW_CONTROLLER_H_
 
 #include <memory>
 
 #include "components/mus/public/cpp/window_observer.h"
@@ skipping 61 matching lines @@
 
  private:
   explicit RootWindowController(WindowManagerApplication* app);
   ~RootWindowController() override;
 
   void AddAccelerators();
 
   // WindowTreeDelegate:
   void OnEmbed(mus::Window* root) override;
   void OnConnectionLost(mus::WindowTreeConnection* connection) override;
-  void OnEventObserved(const ui::Event& event) override;
+  void OnEventObserved(const ui::Event& event,
+                       mus::Window* target) override;
 
   // mus::WindowObserver:
   void OnWindowDestroyed(mus::Window* window) override;
 
   // Sets up the window containers used for z-space management.
   void CreateContainer(mash::wm::mojom::Container container,
                        mash::wm::mojom::Container parent_container);
   void CreateContainers();
 
   WindowManagerApplication* app_;
   mus::Window* root_;
   int window_count_;
 
   std::unique_ptr<WindowManager> window_manager_;
 
   std::map<mus::Window*, std::unique_ptr<LayoutManager>> layout_manager_;
 
   std::unique_ptr<ShadowController> shadow_controller_;
 
   mus::mojom::DisplayPtr display_;
 
   DISALLOW_COPY_AND_ASSIGN(RootWindowController);
 };
 
 }  // namespace wm
 }  // namespace mash
 
 #endif  // MASH_WM_ROOT_WINDOW_CONTROLLER_H_