Prevent overlay scrollbars expand or hover together

cc/input/single_scrollbar_animation_controller_thinning.h

Index: cc/input/single_scrollbar_animation_controller_thinning.h
diff --git a/cc/input/scrollbar_animation_controller_thinning.h b/cc/input/single_scrollbar_animation_controller_thinning.h
similarity index 50%
copy from cc/input/scrollbar_animation_controller_thinning.h
copy to cc/input/single_scrollbar_animation_controller_thinning.h
index 236e595ea263ec5d9f090d913005b34bfbbcd967..b9743874b844ed980191be7b0fa46540a3e9bd8d 100644
--- a/cc/input/scrollbar_animation_controller_thinning.h
+++ b/cc/input/single_scrollbar_animation_controller_thinning.h
@@ -2,76 +2,83 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-#ifndef CC_INPUT_SCROLLBAR_ANIMATION_CONTROLLER_THINNING_H_
-#define CC_INPUT_SCROLLBAR_ANIMATION_CONTROLLER_THINNING_H_
+#ifndef CC_INPUT_SINGLE_SCROLLBAR_ANIMATION_CONTROLLER_THINNING_H_
+#define CC_INPUT_SINGLE_SCROLLBAR_ANIMATION_CONTROLLER_THINNING_H_
 
 #include <memory>
 
 #include "base/macros.h"
+#include "base/time/time.h"
 #include "cc/base/cc_export.h"
-#include "cc/input/scrollbar_animation_controller.h"
+#include "cc/input/scrollbar.h"
+#include "cc/layers/layer_impl.h"
+#include "cc/layers/scrollbar_layer_impl_base.h"
+#include "ui/gfx/geometry/vector2d_f.h"
 
 namespace cc {
 
-// Scrollbar animation that partially fades and thins after an idle delay,
-// and reacts to mouse movements.
-class CC_EXPORT ScrollbarAnimationControllerThinning
-    : public ScrollbarAnimationController {
+class ScrollbarAnimationControllerClient;
+
+// ScrollbarAnimationControllerThinning for one scrollbar
+class CC_EXPORT SingleScrollbarAnimationControllerThinning {
  public:
-  static std::unique_ptr<ScrollbarAnimationControllerThinning> Create(
+  static std::unique_ptr<SingleScrollbarAnimationControllerThinning> Create(
       int scroll_layer_id,
+      ScrollbarOrientation orientation,
       ScrollbarAnimationControllerClient* client,
-      base::TimeDelta delay_before_starting,
-      base::TimeDelta resize_delay_before_starting,
-      base::TimeDelta fade_duration,
       base::TimeDelta thinning_duration);
 
-  ~ScrollbarAnimationControllerThinning() override;
+  ~SingleScrollbarAnimationControllerThinning() {}
 
   void set_mouse_move_distance_for_test(float distance) {
     mouse_move_distance_to_trigger_animation_ = distance;
   }
   bool mouse_is_over_scrollbar() const { return mouse_is_over_scrollbar_; }
   bool mouse_is_near_scrollbar() const { return mouse_is_near_scrollbar_; }
+  bool captured() const { return captured_; }
+
+  bool Animate(base::TimeTicks now);
+  void StartAnimation();
+  void StopAnimation();
 
-  void DidScrollUpdate(bool on_resize) override;
-  void DidScrollEnd() override;
+  void UpdateThumbThicknessScale();
 
-  void DidMouseDown() override;
-  void DidMouseUp() override;
-  void DidMouseLeave() override;
-  void DidMouseMoveNear(float distance) override;
-  bool ScrollbarsHidden() const override;
+  void DidMouseDown();
+  void DidMouseUp();
+  void DidMouseLeave();
+  void DidMouseMoveNear(float distance);
 
- protected:
-  ScrollbarAnimationControllerThinning(
+ private:
+  SingleScrollbarAnimationControllerThinning(
       int scroll_layer_id,
+      ScrollbarOrientation orientation,
       ScrollbarAnimationControllerClient* client,
-      base::TimeDelta delay_before_starting,
-      base::TimeDelta resize_delay_before_starting,
-      base::TimeDelta fade_duration,
       base::TimeDelta thinning_duration);
 
-  void RunAnimationFrame(float progress) override;
-  const base::TimeDelta& Duration() override;
+  float AnimationProgressAtTime(base::TimeTicks now);
+  void RunAnimationFrame(float progress);
+  const base::TimeDelta& Duration();
 
- private:
   // Describes whether the current animation should INCREASE (thicken)
   // a bar or DECREASE it (thin).
   enum AnimationChange { NONE, INCREASE, DECREASE };
-  enum AnimatingProperty { OPACITY, THICKNESS };
   float ThumbThicknessScaleAt(float progress);
+
   float AdjustScale(float new_value,
                     float current_value,
                     AnimationChange animation_change,
                     float min_value,
                     float max_value);
-  void ApplyOpacity(float opacity);
   void ApplyThumbThicknessScale(float thumb_thickness_scale);
 
-  void SetCurrentAnimatingProperty(AnimatingProperty property);
+  ScrollbarAnimationControllerClient* client_;
+
+  base::TimeTicks last_awaken_time_;
+  bool is_animating_;
 
-  float opacity_;
+  int scroll_layer_id_;
+
+  ScrollbarOrientation orientation_;
   bool captured_;
   bool mouse_is_over_scrollbar_;
   bool mouse_is_near_scrollbar_;
@@ -80,14 +87,11 @@ class CC_EXPORT ScrollbarAnimationControllerThinning
   // How close should the mouse be to the scrollbar before we thicken it.
   float mouse_move_distance_to_trigger_animation_;
 
-  base::TimeDelta fade_duration_;
   base::TimeDelta thinning_duration_;
 
-  AnimatingProperty current_animating_property_;
-
-  DISALLOW_COPY_AND_ASSIGN(ScrollbarAnimationControllerThinning);
+  DISALLOW_COPY_AND_ASSIGN(SingleScrollbarAnimationControllerThinning);
 };
 
 }  // namespace cc
 
-#endif  // CC_INPUT_SCROLLBAR_ANIMATION_CONTROLLER_THINNING_H_
+#endif  // CC_INPUT_SINGLE_SCROLLBAR_ANIMATION_CONTROLLER_THINNING_H_