Keep dedicated layers for hiding animation

ui/views/corewm/window_animations.h

Index: ui/views/corewm/window_animations.h
diff --git a/ui/views/corewm/window_animations.h b/ui/views/corewm/window_animations.h
index f5728e6add64fc4ad60b8244540c8c6c28efec62..615017f4d5bb6712d4de13b65748c0e0fb038f6e 100644
--- a/ui/views/corewm/window_animations.h
+++ b/ui/views/corewm/window_animations.h
@@ -7,6 +7,7 @@
 
 #include <vector>
 
+#include "base/memory/scoped_ptr.h"
 #include "ui/views/views_export.h"
 
 namespace aura {
@@ -22,6 +23,7 @@ namespace ui {
 class ImplicitAnimationObserver;
 class Layer;
 class LayerAnimationSequence;
+class ScopedLayerAnimationSettings;
 }
 
 namespace views {
@@ -81,12 +83,46 @@ VIEWS_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.
-VIEWS_EXPORT ui::ImplicitAnimationObserver* CreateHidingWindowAnimationObserver(
-    aura::Window* window);
+class DetachAndRecreateLayersAnimationObserver;
+// A scoped object which detaches the current layers which will animate, and
+// recreates new layers for the window upon deletion of this object.
+// Layers are owned by the animation observer that is added to the
+// detached layer's animator, and will be deleted when the animation
+// is completed. This is intended to be a return value of
+// DetachAndRecreateLayersForHidingAnimation() and not to be created by
+// a client code.
+class LayerDetacherForHidingAnimation {
+ public:
+  LayerDetacherForHidingAnimation(
+      aura::Window* window,
+      ui::ScopedLayerAnimationSettings* settings);
+  ~LayerDetacherForHidingAnimation();
+
+ private:
+  DetachAndRecreateLayersAnimationObserver* observer_;
+
+  DISALLOW_COPY_AND_ASSIGN(LayerDetacherForHidingAnimation);
+};
+
+// This is used to make sure the hiding animation is visible even if
+// the activation changes.
+// This should be called before applying animatinos to |settings|

[sky, 2014/03/11 19:16:23]

animatinos->animations

+// as this installs an animation observer and the returned object should
+// have the same scope as |settings|.
+VIEWS_EXPORT scoped_ptr<LayerDetacherForHidingAnimation>
+    DetachAndRecreateLayersForHidingAnimation(
+        aura::Window* window,
+        ui::ScopedLayerAnimationSettings* settings) WARN_UNUSED_RESULT;
+
+// This installs a window observer that takes ownership of the layers
+// associated with a winddow. This is used to make sure that the

[sky, 2014/03/11 19:16:23]

winddow->window

+// hiding animation can continue after the window has been destroyed.
+// this will install an animation observer.

[sky, 2014/03/11 19:16:23]

this->THis

+// This should be called before applying animatinos to |settings| as
+// this installs an animation observer.
+VIEWS_EXPORT void DetachLayersForHidingAnimationWhenDestroyed(
+    aura::Window* window,
+    ui::ScopedLayerAnimationSettings* settings);
 
 // Returns false if the |window| didn't animate.
 VIEWS_EXPORT bool AnimateOnChildWindowVisibilityChanged(aura::Window* window,