Prevent create ScrollbarAnimationController for Mac Overlay Scrollbar

cc/layers/painted_scrollbar_layer_impl.cc

Index: cc/layers/painted_scrollbar_layer_impl.cc
diff --git a/cc/layers/painted_scrollbar_layer_impl.cc b/cc/layers/painted_scrollbar_layer_impl.cc
index 3abad0dd27505c4fd09db48a58a684d21e0c67a4..6e6db9f91f73d8e8af7d40deb339a5ebfa54c211 100644
--- a/cc/layers/painted_scrollbar_layer_impl.cc
+++ b/cc/layers/painted_scrollbar_layer_impl.cc
@@ -209,4 +209,9 @@ const char* PaintedScrollbarLayerImpl::LayerTypeAsString() const {
   return "cc::PaintedScrollbarLayerImpl";
 }
 
+LayerTreeSettings::ScrollbarAnimator
+PaintedScrollbarLayerImpl::GetScrollbarAnimator() const {
+  return LayerTreeSettings::NO_ANIMATOR;
+}
+
 }  // namespace cc