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

ui/views/animation/ink_drop_hover.h

 // Copyright 2015 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_HOVER_H_
 #define UI_VIEWS_ANIMATION_INK_DROP_HOVER_H_
 
 #include <memory>
 
 #include "base/macros.h"
 #include "base/time/time.h"
 #include "third_party/skia/include/core/SkColor.h"
 #include "ui/gfx/geometry/point.h"
 #include "ui/gfx/geometry/point_f.h"
 #include "ui/gfx/geometry/size.h"
 #include "ui/gfx/transform.h"
 #include "ui/views/views_export.h"
 
 namespace ui {
 class Layer;
 class CallbackLayerAnimationObserver;
 }  // namespace ui
 
 namespace views {
 namespace test {
 class InkDropHoverTestApi;
 }  // namespace test
 
 class RoundedRectangleLayerDelegate;
+class InkDropHoverObserver;
 
 // Manages fade in/out animations for a painted Layer that is used to provide
 // visual feedback on ui::Views for mouse hover states.
 class VIEWS_EXPORT InkDropHover {
  public:
+  enum AnimationType { FADE_IN, FADE_OUT };
+
   InkDropHover(const gfx::Size& size,
                int corner_radius,
                const gfx::Point& center_point,
                SkColor color);
   virtual ~InkDropHover();
 
+  void set_observer(InkDropHoverObserver* observer) { observer_ = observer; }
+
   void set_explode_size(const gfx::Size& size) { explode_size_ = size; }
 
   // Returns true if the hover animation is either in the process of fading
   // in or is fully visible.
   bool IsFadingInOrVisible() const;
 
   // Fades in the hover visual over the given |duration|.
   void FadeIn(const base::TimeDelta& duration);
 
   // Fades out the hover visual over the given |duration|. If |explode| is true
   // then the hover will animate a size increase in addition to the fade out.
   void FadeOut(const base::TimeDelta& duration, bool explode);
 
   // The root Layer that can be added in to a Layer tree.
   ui::Layer* layer() { return layer_.get(); }
 
   // Returns a test api to access internals of this. Default implmentations
   // should return nullptr and test specific subclasses can override to return
   // an instance.
   virtual test::InkDropHoverTestApi* GetTestApi();
 
  private:
   friend class test::InkDropHoverTestApi;
 
-  enum HoverAnimationType { FADE_IN, FADE_OUT };
-
   // Animates a fade in/out as specified by |animation_type| combined with a
   // transformation from the |initial_size| to the |target_size| over the given
   // |duration|.
-  void AnimateFade(HoverAnimationType animation_type,
+  void AnimateFade(AnimationType animation_type,
                    const base::TimeDelta& duration,
                    const gfx::Size& initial_size,
                    const gfx::Size& target_size);
 
   // Calculates the Transform to apply to |layer_| for the given |size|.
   gfx::Transform CalculateTransform(const gfx::Size& size) const;
 
+  // The callback that will be invoked when a fade in/out animation is started.
+  void AnimationStartedCallback(
+      AnimationType animation_type,
+      const ui::CallbackLayerAnimationObserver& observer);
+
   // The callback that will be invoked when a fade in/out animation is complete.
   bool AnimationEndedCallback(
-      HoverAnimationType animation_type,
+      AnimationType animation_type,
       const ui::CallbackLayerAnimationObserver& observer);
 
   // The size of the hover shape when fully faded in.
   gfx::Size size_;
 
   // The target size of the hover shape when it expands during a fade out
   // animation.
   gfx::Size explode_size_;
 
   // The center point of the hover shape in the parent Layer's coordinate space.
   gfx::PointF center_point_;
 
   // True if the last animation to be initiated was a FADE_IN, and false
   // otherwise.
   bool last_animation_initiated_was_fade_in_;
 
   // The LayerDelegate that paints the hover |layer_|.
   std::unique_ptr<RoundedRectangleLayerDelegate> layer_delegate_;
 
   // The visual hover layer that is painted by |layer_delegate_|.
   std::unique_ptr<ui::Layer> layer_;
 
+  InkDropHoverObserver* observer_;
+
   DISALLOW_COPY_AND_ASSIGN(InkDropHover);
 };
 
 }  // namespace views
 
 #endif  // UI_VIEWS_ANIMATION_INK_DROP_HOVER_H_