[ash-md] Animates ToggleButton highlight to move it in sync with the thumb

ui/views/controls/button/toggle_button.h

Index: ui/views/controls/button/toggle_button.h
diff --git a/ui/views/controls/button/toggle_button.h b/ui/views/controls/button/toggle_button.h
index 347d1d050a3e99dbb6ef0625ec8d88ddc0b09173..442f3fbdcd7486350aa5b36e5eb15b77363c2904 100644
--- a/ui/views/controls/button/toggle_button.h
+++ b/ui/views/controls/button/toggle_button.h
@@ -22,11 +22,15 @@ class VIEWS_EXPORT ToggleButton : public CustomButton {
   bool is_on() const { return is_on_; }
 
  private:
+  class ThumbView;
+
   // CustomButton:
   gfx::Size GetPreferredSize() const override;
   void OnPaint(gfx::Canvas* canvas) override;
   void NotifyClick(const ui::Event& event) override;
   void OnNativeThemeChanged(const ui::NativeTheme* theme) override;
+  void AddInkDropLayer(ui::Layer* ink_drop_layer) override;
+  void RemoveInkDropLayer(ui::Layer* ink_drop_layer) override;
   std::unique_ptr<InkDropRipple> CreateInkDropRipple() const override;
   SkColor GetInkDropBaseColor() const override;
   bool ShouldShowInkDropHighlight() const override;
@@ -40,6 +44,9 @@ class VIEWS_EXPORT ToggleButton : public CustomButton {
   bool is_on_;
   gfx::SlideAnimation slide_animation_;
 
+  // A view representing the thumb when ink drop animation is active.
+  std::unique_ptr<ThumbView> thumb_view_;
+
   DISALLOW_COPY_AND_ASSIGN(ToggleButton);
 };