[ash-md] Animates overview shield in and out

ash/common/wm/overview/window_selector_delegate.h

 // Copyright 2013 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.
 
 #ifndef ASH_COMMON_WM_OVERVIEW_WINDOW_SELECTOR_DELEGATE_H_
 #define ASH_COMMON_WM_OVERVIEW_WINDOW_SELECTOR_DELEGATE_H_
 
 #include "ash/ash_export.h"
 #include "base/compiler_specific.h"
 
-namespace aura {
-class Window;
-}
+namespace ash {
 
-namespace ash {
+class WindowSelectorDelegate;
+
+class ASH_EXPORT DelayedAnimationObserver {
+ public:
+  virtual ~DelayedAnimationObserver() {}
+
+  // Sets a |delegate| that can be notified when |this| observer completes
+  // animation.
+  virtual void SetDelegate(WindowSelectorDelegate* delegate) = 0;
+
+  // Can be called by the |delegate| to delete the owned widget.

[bruthig, 2016/07/15 17:05:38]

Is it true that if the owner of |this| calls shutdown that they are then
responsible for deleting the instance?  It appears to be a contract of the API
and is worthy of documentation.

[varkha, 2016/07/15 18:53:36]

Done.

+  virtual void Shutdown() = 0;
+};
 
 // Implement this class to handle the selection event from WindowSelector.
 class ASH_EXPORT WindowSelectorDelegate {
  public:
   // Invoked if selection is ended.
   virtual void OnSelectionEnded() = 0;
 
+  // Passes ownership of |animation_observer| to |this| delegate.
+  virtual void AddDelayedAnimationObserver(

[bruthig, 2016/07/15 17:05:38]

Instead of overloading the WindowSelectorDelegate, would it make more sense to
introduce a DelayedAnimationObserverOwner interface instead.  IMO this would
certainly make the types and variable names in
CleanupWidgetAfterAnimationObserver a lot more understandable.

Or maybe even just renaming CleanupWidgetAfterAnimationObserver::SetDelegate()
to SetOwner() might make it a lot more understandable.

[varkha, 2016/07/15 18:53:36]

I like the last suggestion. Done.

+      std::unique_ptr<DelayedAnimationObserver> animation_observer) = 0;
+
+  // Finds and erases |animation_observer| from the list deleting the widget
+  // owned by the |animation_observer|.
+  virtual void RemoveDelayedAnimationObserver(
+      DelayedAnimationObserver* animation_observer) = 0;
+
  protected:
   virtual ~WindowSelectorDelegate() {}
 };
 
 }  // namespace ash
 
 #endif  // ASH_COMMON_WM_OVERVIEW_WINDOW_SELECTOR_DELEGATE_H_