chromeos: Move files in //ash/common to //ash, part 3

ash/wm_transient_window_observer.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_TRANSIENT_WINDOW_OBSERVER_H_
-#define ASH_COMMON_WM_TRANSIENT_WINDOW_OBSERVER_H_
+#ifndef ASH_WM_TRANSIENT_WINDOW_OBSERVER_H_
+#define ASH_WM_TRANSIENT_WINDOW_OBSERVER_H_
 
 #include "ash/ash_export.h"
 
 namespace ash {
 
 class WmWindow;
 
 class ASH_EXPORT WmTransientWindowObserver {
  public:
   virtual void OnTransientChildAdded(WmWindow* window, WmWindow* transient) {}
   virtual void OnTransientChildRemoved(WmWindow* window, WmWindow* transient) {}
 
  protected:
   virtual ~WmTransientWindowObserver() {}
 };
 
 }  // namespace ash
 
-#endif  // ASH_COMMON_WM_TRANSIENT_WINDOW_OBSERVER_H_
+#endif  // ASH_WM_TRANSIENT_WINDOW_OBSERVER_H_