Fixed rounding issue on scrollbar rasterization.

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 "cc/resources/resource_update_queue.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);
+    int scrolling_layer_id,
+    FakeScrollbar* fake_scrollbar) {
+  if (!fake_scrollbar)
+    fake_scrollbar = new FakeScrollbar(paint_during_update, has_thumb, false);
   return make_scoped_refptr(new FakePaintedScrollbarLayer(
       fake_scrollbar, scrolling_layer_id));
 }
 
 FakePaintedScrollbarLayer::FakePaintedScrollbarLayer(
     FakeScrollbar* fake_scrollbar,
     int scrolling_layer_id)
     : PaintedScrollbarLayer(scoped_ptr<Scrollbar>(fake_scrollbar).Pass(),
                             scrolling_layer_id),
       update_count_(0),
@@ skipping 18 matching lines @@
   ++push_properties_count_;
 }
 
 scoped_ptr<base::AutoReset<bool> >
 FakePaintedScrollbarLayer::IgnoreSetNeedsCommit() {
   return make_scoped_ptr(
       new base::AutoReset<bool>(&ignore_set_needs_commit_, true));
 }
 
 }  // namespace cc