Keep dedicated layers for hiding animation

ui/wm/core/window_animations.h

Index: ui/wm/core/window_animations.h
diff --git a/ui/wm/core/window_animations.h b/ui/wm/core/window_animations.h
index 2c7997d9538a647ba306e278cd304a1ab8905ba3..ae1295bdb45a1591f897f3ce1c4bb6149a06c1d2 100644
--- a/ui/wm/core/window_animations.h
+++ b/ui/wm/core/window_animations.h
@@ -7,6 +7,7 @@
 
 #include <vector>
 
+#include "ui/compositor/scoped_layer_animation_settings.h"
 #include "ui/wm/core/wm_core_export.h"
 
 namespace aura {
@@ -81,12 +82,39 @@ WM_CORE_EXPORT void SetWindowVisibilityAnimationVerticalPosition(
     aura::Window* window,
     float position);
 
-// Creates an ImplicitAnimationObserver that takes ownership of the layers
-// associated with a Window so that the animation can continue after the Window
-// has been destroyed.
-// The returned object deletes itself when the animations are done.
-WM_CORE_EXPORT ui::ImplicitAnimationObserver*
-    CreateHidingWindowAnimationObserver(aura::Window* window);
+// A wrapper of ui::ScopedLayerAnimationSettings for hiding animations.
+// Use this to ensure that the animation is visible even after
+// the window is deleted, instead of directly using
+// ui::ScopedLayerAnimationSettings.
+class WM_CORE_EXPORT ScopedHidingAnimationSettings {
+ public:
+  explicit ScopedHidingAnimationSettings(aura::Window* window);
+  ~ScopedHidingAnimationSettings();
+
+  // Returns the wrapped ScopedLayeAnimationSettings instance.
+  ui::ScopedLayerAnimationSettings* layer_animation_settings() {
+    return &layer_animation_settings_;
+  }
+
+  // When set to true, this recreates layers for the window and and puts
+  // the original (and animating) layers on top of |window_| and
+  // its transient children so that these layers stay above new
+  // focused window. This is typically used when closing a focusable
+  // toplevel window.
+  // Note that this is effective only if |window| has focus when
+  // applying the animation.
+  void set_ensure_visible_after_focus_lost(
+      bool ensure_visible_after_focus_loste) {
+    ensure_visibility_after_focus_lost_ = ensure_visible_after_focus_lost;
+  }
+
+ private:
+  aura::Window* window_;
+  bool ensure_visibility_after_focus_lost_;
+  ui::ScopedLayerAnimationSettings layer_animation_settings_;
+
+  DISALLOW_COPY_AND_ASSIGN(ScopedHidingAnimationSettings);
+};
 
 // Returns false if the |window| didn't animate.
 WM_CORE_EXPORT bool AnimateOnChildWindowVisibilityChanged(aura::Window* window,