Left side vertical MD scrollbars grow toward right.

cc/test/fake_painted_scrollbar_layer.h

Index: cc/test/fake_painted_scrollbar_layer.h
diff --git a/cc/test/fake_painted_scrollbar_layer.h b/cc/test/fake_painted_scrollbar_layer.h
index 3391797a8577093069b7dc6edd9b448f9a0383dc..bbb38cdfb8fad9c9260b61c0f990e0195f92fedc 100644
--- a/cc/test/fake_painted_scrollbar_layer.h
+++ b/cc/test/fake_painted_scrollbar_layer.h
@@ -22,6 +22,13 @@ class FakePaintedScrollbarLayer : public PaintedScrollbarLayer {
       bool paint_during_update,
       bool has_thumb,
       int scrolling_layer_id);
+  static scoped_refptr<FakePaintedScrollbarLayer> Create(
+      bool paint_during_update,
+      bool has_thumb,
+      ScrollbarOrientation orientation,
+      bool is_left_side_vertical_scrollbar,
+      bool is_overlay,
+      int scrolling_layer_id);
   int update_count() const { return update_count_; }
   void reset_update_count() { update_count_ = 0; }