[mus+ash] Removes WmWindow from ash/wm/overview and ash/wm/workspace

ash/wm/workspace/workspace_event_handler_aura.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_WM_WORKSPACE_WORKSPACE_EVENT_HANDLER_AURA_H_
 #define ASH_WM_WORKSPACE_WORKSPACE_EVENT_HANDLER_AURA_H_
 
 #include "ash/ash_export.h"
 #include "ash/wm/workspace/workspace_event_handler.h"
 #include "base/macros.h"
 #include "ui/events/event_handler.h"
 
+namespace aura {
+class Window;
+}
+
 namespace ash {
 
-class WmWindow;
-
 class ASH_EXPORT WorkspaceEventHandlerAura : public ui::EventHandler,
                                              public WorkspaceEventHandler {
  public:
-  explicit WorkspaceEventHandlerAura(WmWindow* workspace_window);
+  explicit WorkspaceEventHandlerAura(aura::Window* workspace_window);
   ~WorkspaceEventHandlerAura() override;
 
   // ui::EventHandler:
   void OnMouseEvent(ui::MouseEvent* event) override;
   void OnGestureEvent(ui::GestureEvent* event) override;
 
  private:
-  WmWindow* workspace_window_;
+  aura::Window* workspace_window_;
 
   DISALLOW_COPY_AND_ASSIGN(WorkspaceEventHandlerAura);
 };
 
 }  // namespace ash
 
 #endif  // ASH_WM_WORKSPACE_WORKSPACE_EVENT_HANDLER_AURA_H_