Moves ash/wm/common back into ash

ash/wm/common/wm_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_WM_COMMON_WM_WINDOW_OBSERVER_H_
 #define ASH_WM_COMMON_WM_WINDOW_OBSERVER_H_
 
 #include <stdint.h>
 
-#include "ash/wm/common/ash_wm_common_export.h"
+#include "ash/ash_export.h"
 
 namespace gfx {
 class Rect;
 }
 
 namespace ash {
 namespace wm {
 
 class WmWindow;
 enum class WmWindowProperty;
 
-class ASH_WM_COMMON_EXPORT WmWindowObserver {
+class ASH_EXPORT WmWindowObserver {
  public:
   struct TreeChangeParams {
     WmWindow* target = nullptr;
     WmWindow* old_parent = nullptr;
     WmWindow* new_parent = nullptr;
   };
 
   // |window| is the window the observer was added to, which is not necessarily
   // the window that was added/removed.
   virtual void OnWindowTreeChanged(WmWindow* window,
@@ skipping 13 matching lines @@
   virtual void OnWindowVisibilityChanging(wm::WmWindow* window, bool visible) {}
 
  protected:
   virtual ~WmWindowObserver() {}
 };
 
 }  // namespace wm
 }  // namespace ash
 
 #endif  // ASH_WM_COMMON_WM_WINDOW_OBSERVER_H_