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

cc/trees/layer_tree_host_impl.cc

Index: cc/trees/layer_tree_host_impl.cc
diff --git a/cc/trees/layer_tree_host_impl.cc b/cc/trees/layer_tree_host_impl.cc
index 4aa0886dfb80d80425acf157f5d0e7d8daf1e872..20cbf21de6e32c0b379309fdad193c53e6e8f2af 100644
--- a/cc/trees/layer_tree_host_impl.cc
+++ b/cc/trees/layer_tree_host_impl.cc
@@ -209,6 +209,7 @@ LayerTreeHostImpl::LayerTreeHostImpl(
       wheel_scrolling_(false),
       scroll_affects_scroll_handler_(false),
       scroll_layer_id_when_mouse_over_scrollbar_(Layer::INVALID_ID),
+      scroll_layer_id_when_mouse_near_scrollbar_(Layer::INVALID_ID),
       captured_scrollbar_layer_id_(Layer::INVALID_ID),
       tile_priorities_dirty_(false),
       settings_(settings),
@@ -3232,6 +3233,7 @@ void LayerTreeHostImpl::MouseUp() {
 }
 
 void LayerTreeHostImpl::MouseMoveAt(const gfx::Point& viewport_point) {
+  scroll_layer_id_when_mouse_near_scrollbar_ = Layer::INVALID_ID;
   gfx::PointF device_viewport_point = gfx::ScalePoint(
       gfx::PointF(viewport_point), active_tree_->device_scale_factor());
   LayerImpl* layer_impl =
@@ -3255,6 +3257,8 @@ void LayerTreeHostImpl::MouseMoveAt(const gfx::Point& viewport_point) {
   if (!animation_controller)
     return;
 
+  scroll_layer_id_when_mouse_near_scrollbar_ = scroll_layer_impl->id();
+
   float distance_to_scrollbar = std::numeric_limits<float>::max();
   for (ScrollbarLayerImplBase* scrollbar :
        ScrollbarsFor(scroll_layer_impl->id()))
@@ -3266,6 +3270,24 @@ void LayerTreeHostImpl::MouseMoveAt(const gfx::Point& viewport_point) {
                                          active_tree_->device_scale_factor());
 }
 
+void LayerTreeHostImpl::MouseLeave() {
+  // scroll_layer_id_when_mouse_near_scrollbar_ and
+  // scroll_layer_id_when_mouse_over_scrollbar_ should not be both true
+  DCHECK(scroll_layer_id_when_mouse_near_scrollbar_ == Layer::INVALID_ID ||
+         scroll_layer_id_when_mouse_over_scrollbar_ == Layer::INVALID_ID);
+
+  int scroll_layer_id =
+      scroll_layer_id_when_mouse_near_scrollbar_ != Layer::INVALID_ID
+          ? scroll_layer_id_when_mouse_near_scrollbar_
+          : scroll_layer_id_when_mouse_over_scrollbar_;
+
+  ScrollbarAnimationController* animation_controller =
+      ScrollbarAnimationControllerForId(scroll_layer_id);
+
+  if (animation_controller)
+    animation_controller->DidMouseLeave();
+}
+
 void LayerTreeHostImpl::HandleMouseOverScrollbar(LayerImpl* layer_impl) {
   int new_id = Layer::INVALID_ID;
   if (layer_impl && layer_impl->ToScrollbarLayer())