Overlay scrollbars shouldn't fade out while mouse is over/near.

cc/input/scrollbar_animation_controller_thinning.h

Index: cc/input/scrollbar_animation_controller_thinning.h
diff --git a/cc/input/scrollbar_animation_controller_thinning.h b/cc/input/scrollbar_animation_controller_thinning.h
index 0b393088b89c209f5771c617781c4bce7a264f89..236e595ea263ec5d9f090d913005b34bfbbcd967 100644
--- a/cc/input/scrollbar_animation_controller_thinning.h
+++ b/cc/input/scrollbar_animation_controller_thinning.h
@@ -35,6 +35,7 @@ class CC_EXPORT ScrollbarAnimationControllerThinning
   bool mouse_is_near_scrollbar() const { return mouse_is_near_scrollbar_; }
 
   void DidScrollUpdate(bool on_resize) override;
+  void DidScrollEnd() override;
 
   void DidMouseDown() override;
   void DidMouseUp() override;