Keep dedicated layers for hiding animation

ash/wm/window_animations.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/window_animations.h"
 
 #include <math.h>
 
 #include <algorithm>
 #include <vector>
@@ skipping 158 matching lines @@
 }
 
 void AnimateHideWindow_Minimize(aura::Window* window) {
   window->layer()->set_delegate(NULL);
 
   // Property sets within this scope will be implicitly animated.
   ui::ScopedLayerAnimationSettings settings(window->layer()->GetAnimator());
   base::TimeDelta duration = base::TimeDelta::FromMilliseconds(
       kLayerAnimationsForMinimizeDurationMS);
   settings.SetTransitionDuration(duration);
-  settings.AddObserver(
-      views::corewm::CreateHidingWindowAnimationObserver(window));
+  scoped_ptr<views::corewm::LayerDetacherForHidingAnimation> detacher =
+      views::corewm::DetachAndRecreateLayersForHidingAnimation(
+          window, &settings).Pass();
   window->layer()->SetVisible(false);
 
   AddLayerAnimationsForMinimize(window, false);
 }
 
 void AnimateShowHideWindowCommon_BrightnessGrayscale(aura::Window* window,
                                                      bool show) {
   window->layer()->set_delegate(window);
 
   float start_value, end_value;
@@ skipping 11 matching lines @@
     window->layer()->SetOpacity(kWindowAnimation_ShowOpacity);
     window->layer()->SetVisible(true);
   }
 
   base::TimeDelta duration =
       base::TimeDelta::FromMilliseconds(kBrightnessGrayscaleFadeDurationMs);
 
   ui::ScopedLayerAnimationSettings settings(window->layer()->GetAnimator());
   settings.SetTransitionDuration(duration);
   if (!show) {
-    settings.AddObserver(
-        views::corewm::CreateHidingWindowAnimationObserver(window));
+    views::corewm::DetachLayersForHidingAnimationWhenDestroyed(
+        window, &settings);
   }
 
   window->layer()->GetAnimator()->
       ScheduleTogether(
           CreateBrightnessGrayscaleAnimationSequence(end_value, duration));
   if (!show) {
     window->layer()->SetOpacity(kWindowAnimation_HideOpacity);
     window->layer()->SetVisible(false);
   }
 }
@@ skipping 271 matching lines @@
   }
 
   // Assume the shelf is overflowed, zoom off to the bottom right of the
   // work area.
   gfx::Rect work_area =
       Shell::GetScreen()->GetDisplayNearestWindow(window).work_area();
   return gfx::Rect(work_area.right(), work_area.bottom(), 0, 0);
 }
 
 }  // namespace ash