Ash: Fix WM window resize shadow stacking.

ash/wm/resize_shadow.h

 // Copyright (c) 2012 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_RESIZE_SHADOW_H_
 #define ASH_WM_RESIZE_SHADOW_H_
 
 #include <memory>
 
 #include "base/macros.h"
@@ skipping 14 matching lines @@
 class ResizeShadow : public aura::WindowObserver {
  public:
   explicit ResizeShadow(aura::Window* window);
   ~ResizeShadow() override;
 
   // aura::WindowObserver:
   void OnWindowBoundsChanged(aura::Window* window,
                              const gfx::Rect& old_bounds,
                              const gfx::Rect& new_bounds) override;
   void OnWindowHierarchyChanged(const HierarchyChangeParams& params) override;
+  void OnWindowStackingChanged(aura::Window* window) override;
 
   // Shows resize effects for one or more edges based on a |hit_test| code, such
   // as HTRIGHT or HTBOTTOMRIGHT.
   void ShowForHitTest(int hit_test);
 
   // Hides all resize effects.
   void Hide();
 
   int GetLastHitTestForTest() const { return last_hit_test_; }
   const ui::Layer* GetLayerForTest() const { return layer_.get(); }
@@ skipping 14 matching lines @@
   // Hit test value from last call to ShowForHitTest().  Used to prevent
   // repeatedly triggering the same animations for the same hit.
   int last_hit_test_;
 
   DISALLOW_COPY_AND_ASSIGN(ResizeShadow);
 };
 
 }  // namespace ash
 
 #endif  // ASH_WM_RESIZE_SHADOW_H_