Prevent create ScrollbarAnimationController for Mac Overlay Scrollbar

cc/layers/scrollbar_layer_impl_base.h

Index: cc/layers/scrollbar_layer_impl_base.h
diff --git a/cc/layers/scrollbar_layer_impl_base.h b/cc/layers/scrollbar_layer_impl_base.h
index 644557a08f59e23bd1757f3294da86c8779af06b..91dbebee832e956fe9a4794d6a4381fe16881261 100644
--- a/cc/layers/scrollbar_layer_impl_base.h
+++ b/cc/layers/scrollbar_layer_impl_base.h
@@ -11,6 +11,7 @@
 #include "cc/input/scrollbar.h"
 #include "cc/layers/layer.h"
 #include "cc/layers/layer_impl.h"
+#include "cc/trees/layer_tree_settings.h"
 
 namespace cc {
 
@@ -63,6 +64,8 @@ class CC_EXPORT ScrollbarLayerImplBase : public LayerImpl {
   // on overlay scrollbar layers.
   void SetOverlayScrollbarLayerOpacityAnimated(float opacity);
 
+  virtual LayerTreeSettings::ScrollbarAnimator GetScrollbarAnimator() const;
+
  protected:
   ScrollbarLayerImplBase(LayerTreeImpl* tree_impl,
                          int id,