Left side vertical MD scrollbars grow toward right.

cc/test/fake_painted_scrollbar_layer.cc

 // Copyright 2013 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/test/fake_painted_scrollbar_layer.h"
 
 #include "base/auto_reset.h"
 #include "base/memory/ptr_util.h"
 #include "cc/test/fake_scrollbar.h"
 
 namespace cc {
 
 scoped_refptr<FakePaintedScrollbarLayer> FakePaintedScrollbarLayer::Create(
     bool paint_during_update,
     bool has_thumb,
     int scrolling_layer_id) {
-  FakeScrollbar* fake_scrollbar = new FakeScrollbar(
-      paint_during_update, has_thumb, false);
+  return Create(paint_during_update, has_thumb, HORIZONTAL, false, false,
+                scrolling_layer_id);
+}
+
+scoped_refptr<FakePaintedScrollbarLayer> FakePaintedScrollbarLayer::Create(
+    bool paint_during_update,
+    bool has_thumb,
+    ScrollbarOrientation orientation,
+    bool is_left_side_vertical_scrollbar,
+    bool is_overlay,
+    int scrolling_layer_id) {
+  FakeScrollbar* fake_scrollbar =
+      new FakeScrollbar(paint_during_update, has_thumb, orientation,
+                        is_left_side_vertical_scrollbar, is_overlay);
   return make_scoped_refptr(
       new FakePaintedScrollbarLayer(fake_scrollbar, scrolling_layer_id));
 }
 
 FakePaintedScrollbarLayer::FakePaintedScrollbarLayer(
     FakeScrollbar* fake_scrollbar,
     int scrolling_layer_id)
     : PaintedScrollbarLayer(std::unique_ptr<Scrollbar>(fake_scrollbar),
                             scrolling_layer_id),
       update_count_(0),
@@ skipping 16 matching lines @@
   ++push_properties_count_;
 }
 
 std::unique_ptr<base::AutoReset<bool>>
 FakePaintedScrollbarLayer::IgnoreSetNeedsCommit() {
   return base::MakeUnique<base::AutoReset<bool>>(&ignore_set_needs_commit_,
                                                  true);
 }
 
 }  // namespace cc