Added a views::test::TestInkDropAnimationObserverHelper

ui/views/animation/ink_drop_animation.h

 // Copyright 2016 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 UI_VIEWS_ANIMATION_INK_DROP_ANIMATION_H_
 #define UI_VIEWS_ANIMATION_INK_DROP_ANIMATION_H_
 
 #include "base/macros.h"
 #include "ui/gfx/geometry/point.h"
 #include "ui/views/animation/ink_drop_animation_observer.h"
@@ skipping 28 matching lines @@
 
   // The opacity of the ink drop when it is not visible.
   static const float kHiddenOpacity;
 
   // The opacity of the ink drop when it is visible.
   static const float kVisibleOpacity;
 
   InkDropAnimation();
   virtual ~InkDropAnimation();
 
+  // In the event that an animation is in progress for ink drop state 's1' and
+  // an animation to a new state 's2' is triggered, then
+  // AnimationEnded(s1, PRE_EMPTED) will be called before
+  // AnimationStarted(s2).
   void set_observer(InkDropAnimationObserver* observer) {
     observer_ = observer;
   }
 
   // Animates from the current InkDropState to the new |ink_drop_state|.
   //
   // NOTE: GetTargetInkDropState() should return the new |ink_drop_state| value
   // to any observers being notified as a result of the call.
   void AnimateToState(InkDropState ink_drop_state);
 
@@ skipping 50 matching lines @@
   InkDropState target_ink_drop_state_;
 
   InkDropAnimationObserver* observer_;
 
   DISALLOW_COPY_AND_ASSIGN(InkDropAnimation);
 };
 
 }  // namespace views
 
 #endif  // UI_VIEWS_ANIMATION_INK_DROP_ANIMATION_H_