Add MD Ink Drop Layers to InkDropHost only when a ripple/hover is active.

ui/views/animation/test/test_ink_drop_animation_observer.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_TEST_TEST_INK_DROP_ANIMATION_OBSERVER_H_
 #define UI_VIEWS_ANIMATION_TEST_TEST_INK_DROP_ANIMATION_OBSERVER_H_
 
 #include "testing/gtest/include/gtest/gtest.h"
 #include "ui/views/animation/ink_drop_animation_observer.h"
 #include "ui/views/animation/ink_drop_state.h"
@@ skipping 25 matching lines @@
   InkDropState target_state_at_last_animation_ended() const {
     return target_state_at_last_animation_ended_;
   }
 
   // InkDropAnimationObserver:
   void AnimationStarted(InkDropState ink_drop_state) override;
   void AnimationEnded(InkDropState ink_drop_state,
                       InkDropAnimationEndedReason reason) override;
 
  private:
-  // The type as this inherits from. Reduces verbosity in .cc file.
+  // The type this inherits from. Reduces verbosity in .cc file.
   using ObserverHelper = TestInkDropAnimationObserverHelper<InkDropState>;
 
   // The value of InkDropAnimation::GetTargetInkDropState() the last time an
   // InkDropAnimationStarted() event was handled. This is only valid if
   // |ink_drop_animation_| is not null.
   InkDropState target_state_at_last_animation_started_;
 
   // The value of InkDropAnimation::GetTargetInkDropState() the last time an
   // AnimationEnded() event was handled. This is only valid if
   // |ink_drop_animation_| is not null.
   InkDropState target_state_at_last_animation_ended_;
 
   // An InkDropAnimation to spy info from when notifications are handled.
   InkDropAnimation* ink_drop_animation_;
 
   DISALLOW_COPY_AND_ASSIGN(TestInkDropAnimationObserver);
 };
 
 }  // namespace test
 }  // namespace views
 
 #endif  // UI_VIEWS_ANIMATION_TEST_TEST_INK_DROP_ANIMATION_OBSERVER_H_