Use a single ToplevelWindowEventHandler for the ash::Shell

ash/wm/toplevel_window_event_handler.h

Index: ash/wm/toplevel_window_event_handler.h
diff --git a/ash/wm/toplevel_window_event_handler.h b/ash/wm/toplevel_window_event_handler.h
index 98c9296c947ca8caf927d9a2e15637b8316f70d1..06120ac2589b39b5e09fde843b14c13acda7ad5d 100644
--- a/ash/wm/toplevel_window_event_handler.h
+++ b/ash/wm/toplevel_window_event_handler.h
@@ -34,11 +34,9 @@ class ASH_EXPORT ToplevelWindowEventHandler
       public aura::client::WindowMoveClient,
       public DisplayController::Observer {
  public:
-  explicit ToplevelWindowEventHandler(aura::Window* owner);
+  ToplevelWindowEventHandler();
   virtual ~ToplevelWindowEventHandler();
 
-  const aura::Window* owner() const { return owner_; }
-
   // Overridden from ui::EventHandler:
   virtual void OnKeyEvent(ui::KeyEvent* event) OVERRIDE;
   virtual void OnMouseEvent(ui::MouseEvent* event) OVERRIDE;
@@ -88,9 +86,6 @@ class ASH_EXPORT ToplevelWindowEventHandler
   // Invoked from ScopedWindowResizer if the window is destroyed.
   void ResizerWindowDestroyed();
 
-  // The container which this event handler is handling events on.
-  aura::Window* owner_;
-
   // Are we running a nested message loop from RunMoveLoop().
   bool in_move_loop_;