Keep dedicated layers for hiding animation

ash/wm/window_animations.cc

Index: ash/wm/window_animations.cc
diff --git a/ash/wm/window_animations.cc b/ash/wm/window_animations.cc
index a5b36530bfdb7507be582c7aa579ed0c91261ad5..18a6fa10b349e5e19d408a16a8ff6733ce27d022 100644
--- a/ash/wm/window_animations.cc
+++ b/ash/wm/window_animations.cc
@@ -173,12 +173,10 @@ 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());
+  views::corewm::ScopedHidingAnimationSettings hiding_settings(window);
   base::TimeDelta duration = base::TimeDelta::FromMilliseconds(
       kLayerAnimationsForMinimizeDurationMS);
-  settings.SetTransitionDuration(duration);
-  settings.AddObserver(
-      views::corewm::CreateHidingWindowAnimationObserver(window));
+  hiding_settings.layer_animation_settings()->SetTransitionDuration(duration);
   window->layer()->SetVisible(false);
 
   AddLayerAnimationsForMinimize(window, false);
@@ -207,17 +205,16 @@ void AnimateShowHideWindowCommon_BrightnessGrayscale(aura::Window* window,
   base::TimeDelta duration =
       base::TimeDelta::FromMilliseconds(kBrightnessGrayscaleFadeDurationMs);
 
-  ui::ScopedLayerAnimationSettings settings(window->layer()->GetAnimator());
-  settings.SetTransitionDuration(duration);
-  if (!show) {
-    settings.AddObserver(
-        views::corewm::CreateHidingWindowAnimationObserver(window));
-  }
-
-  window->layer()->GetAnimator()->
-      ScheduleTogether(
-          CreateBrightnessGrayscaleAnimationSequence(end_value, duration));
-  if (!show) {
+  if (show) {
+    ui::ScopedLayerAnimationSettings settings(window->layer()->GetAnimator());
+    window->layer()->GetAnimator()->
+        ScheduleTogether(
+            CreateBrightnessGrayscaleAnimationSequence(end_value, duration));
+  } else {
+    views::corewm::ScopedHidingAnimationSettings hiding_settings(window);
+    window->layer()->GetAnimator()->
+        ScheduleTogether(
+            CreateBrightnessGrayscaleAnimationSequence(end_value, duration));
     window->layer()->SetOpacity(kWindowAnimation_HideOpacity);
     window->layer()->SetVisible(false);
   }