Left side vertical MD scrollbars grow toward right.

cc/layers/painted_scrollbar_layer_impl_unittest.cc

 // Copyright 2014 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "cc/layers/painted_scrollbar_layer_impl.h"
 
 #include <stddef.h>
 
 #include "cc/quads/draw_quad.h"
 #include "cc/quads/texture_draw_quad.h"
@@ skipping 23 matching lines @@
   SkBitmap track_sk_bitmap;
   track_sk_bitmap.allocN32Pixels(10, 10);
   track_sk_bitmap.setImmutable();
   UIResourceId track_uid = 6;
   UIResourceBitmap track_bitmap(track_sk_bitmap);
   impl.host_impl()->CreateUIResource(track_uid, track_bitmap);
 
   ScrollbarOrientation orientation = VERTICAL;
 
   PaintedScrollbarLayerImpl* scrollbar_layer_impl =
-      impl.AddChildToRoot<PaintedScrollbarLayerImpl>(orientation);
+      impl.AddChildToRoot<PaintedScrollbarLayerImpl>(orientation, false, false);
   scrollbar_layer_impl->SetBounds(layer_size);
   scrollbar_layer_impl->SetContentsOpaque(true);
   scrollbar_layer_impl->set_internal_contents_scale_and_bounds(
       scale, scaled_layer_size);
   scrollbar_layer_impl->SetDrawsContent(true);
   scrollbar_layer_impl->SetThumbThickness(layer_size.width());
   scrollbar_layer_impl->SetThumbLength(500);
   scrollbar_layer_impl->SetTrackLength(layer_size.height());
   scrollbar_layer_impl->SetCurrentPos(100.f / 4);
   scrollbar_layer_impl->SetClipLayerLength(100.f);
@@ skipping 69 matching lines @@
     LayerTestCommon::VerifyQuadsAreOccluded(
         impl.quad_list(), occluded, &partially_occluded_count);
     // The layer outputs two quads, which is partially occluded.
     EXPECT_EQ(2u, impl.quad_list().size());
     EXPECT_EQ(2u, partially_occluded_count);
   }
 }
 
 }  // namespace
 }  // namespace cc