Makes WorkspaceLayoutManager use ash/wm/common types

ash/wm/workspace/workspace_layout_manager_backdrop_delegate.h

 // Copyright 2014 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_LAYOUT_MANAGER_BACKDROP_DELEGATE_H_
 #define ASH_WM_WORKSPACE_WORKSPACE_LAYOUT_MANAGER_BACKDROP_DELEGATE_H_
 
 #include "ash/ash_export.h"
 #include "ash/wm/common/wm_types.h"
 
-namespace aura {
-class Window;
-}
-
 namespace ash {
 namespace wm {
 class WindowState;
+class WmWindow;
 }
 
 // A delegate which can be set to create and control a backdrop which gets
 // placed below the top level window.
 class ASH_EXPORT WorkspaceLayoutManagerBackdropDelegate {
  public:
   virtual ~WorkspaceLayoutManagerBackdropDelegate() {}
 
   // A window got added to the layout.
-  virtual void OnWindowAddedToLayout(aura::Window* child) = 0;
+  virtual void OnWindowAddedToLayout(wm::WmWindow* child) = 0;
 
   // A window got removed from the layout.
-  virtual void OnWindowRemovedFromLayout(aura::Window* child) = 0;
+  virtual void OnWindowRemovedFromLayout(wm::WmWindow* child) = 0;
 
   // The visibility of a window has changed.
-  virtual void OnChildWindowVisibilityChanged(aura::Window* child,
+  virtual void OnChildWindowVisibilityChanged(wm::WmWindow* child,
                                               bool visible) = 0;
 
   // The stacking order of a window has changed.
-  virtual void OnWindowStackingChanged(aura::Window* window) = 0;
+  virtual void OnWindowStackingChanged(wm::WmWindow* window) = 0;
 
   // A window state type has changed.
   virtual void OnPostWindowStateTypeChange(wm::WindowState* window_state,
                                            wm::WindowStateType old_type) = 0;
 
   // The work area insets have changed, altering the total available space.
   virtual void OnDisplayWorkAreaInsetsChanged() = 0;
 };
 
 }  // namespace ash
 
 #endif  // ASH_WM_WORKSPACE_WORKSPACE_LAYOUT_MANAGER_BACKDROP_DELEGATE_H_