Prevent create ScrollbarAnimationController for Mac Overlay Scrollbar

cc/layers/scrollbar_layer_impl_base.cc

Index: cc/layers/scrollbar_layer_impl_base.cc
diff --git a/cc/layers/scrollbar_layer_impl_base.cc b/cc/layers/scrollbar_layer_impl_base.cc
index 5070c84b2e341b1817bcb790702ef360965668f9..681a0401f429afb88e165385860002c4a3214273 100644
--- a/cc/layers/scrollbar_layer_impl_base.cc
+++ b/cc/layers/scrollbar_layer_impl_base.cc
@@ -236,4 +236,9 @@ void ScrollbarLayerImplBase::SetOverlayScrollbarLayerOpacityAnimated(
   layer_tree_impl()->set_needs_update_draw_properties();
 }
 
+LayerTreeSettings::ScrollbarAnimator
+ScrollbarLayerImplBase::GetScrollbarAnimator() const {
+  return layer_tree_impl()->settings().scrollbar_animator;
+}
+
 }  // namespace cc