Ash: Fix WM window resize shadow stacking.

ash/wm/resize_shadow.cc

 // 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.
 
 #include "ash/wm/resize_shadow.h"
 
 #include "base/lazy_instance.h"
 #include "base/time/time.h"
 #include "ui/aura/window.h"
 #include "ui/base/hit_test.h"
@@ skipping 76 matching lines @@
                                          const gfx::Rect& old_bounds,
                                          const gfx::Rect& new_bounds) {
   UpdateBoundsAndVisibility();
 }
 
 void ResizeShadow::OnWindowHierarchyChanged(
     const aura::WindowObserver::HierarchyChangeParams& params) {
   ReparentLayer();
 }
 
+void ResizeShadow::OnWindowStackingChanged(aura::Window* window) {
+  ReparentLayer();
+}
+
 void ResizeShadow::ShowForHitTest(int hit) {
   // Don't start animations unless something changed.
   if (hit == last_hit_test_)
     return;
   last_hit_test_ = hit;
 
   UpdateBoundsAndVisibility();
 }
 
 void ResizeShadow::Hide() {
@@ skipping 37 matching lines @@
     constexpr int kShadowFadeOutDurationMs = 100;
     settings.SetTransitionDuration(
         base::TimeDelta::FromMilliseconds(kShadowFadeOutDurationMs));
   }
   constexpr float kShadowTargetOpacity = 0.5f;
   layer_->SetOpacity(visible ? kShadowTargetOpacity : 0.f);
   layer_->SetVisible(visible);
 }
 
 }  // namespace ash