cancel overlay-scrollbar hover state when moving pointer out of window for ChromeOS

cc/input/scrollbar_animation_controller_thinning.cc

Index: cc/input/scrollbar_animation_controller_thinning.cc
diff --git a/cc/input/scrollbar_animation_controller_thinning.cc b/cc/input/scrollbar_animation_controller_thinning.cc
index 4324a4347bf32943698961ea04265905845f8ff1..a7be16f4ff7812ffc08aa02f7da1e9fb515852d2 100644
--- a/cc/input/scrollbar_animation_controller_thinning.cc
+++ b/cc/input/scrollbar_animation_controller_thinning.cc
@@ -134,6 +134,23 @@ void ScrollbarAnimationControllerThinning::DidMouseMoveNear(float distance) {
   }
 }
 
+void ScrollbarAnimationControllerThinning::DidMouseLeave() {

[aelias_OOO_until_Jul13, 2016/10/07 02:09:51]

This seems very similar to DidMouseMoveOffScrollbar, are the differences
meaningful?  Can't this just be deleted and the caller can use
DidMouseMoveOffScrollbar instead?

[chaopeng, 2016/10/07 15:56:04]

Yes, I should use DidMouseMoveOffScrollbar.

+  if (captured_)
+    return;
+
+  if (mouse_is_over_scrollbar_) {
+    mouse_is_over_scrollbar_ = false;
+    opacity_change_ = DECREASE;
+  }
+
+  if (mouse_is_near_scrollbar_) {
+    mouse_is_near_scrollbar_ = false;
+    thickness_change_ = DECREASE;
+  }
+
+  StartAnimation();
+}
+
 float ScrollbarAnimationControllerThinning::OpacityAtAnimationProgress(
     float progress) {
   if (opacity_change_ == NONE)