Fixed rounding issue on scrollbar rasterization.

cc/test/fake_painted_scrollbar_layer.h

 // 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.
 
 #ifndef CC_TEST_FAKE_PAINTED_SCROLLBAR_LAYER_H_
 #define CC_TEST_FAKE_PAINTED_SCROLLBAR_LAYER_H_
 
 #include "base/memory/scoped_ptr.h"
 #include "cc/layers/painted_scrollbar_layer.h"
 #include "cc/test/fake_scrollbar.h"
 
 namespace base { template<typename T> class AutoReset; }
 
 namespace cc {
 
 class FakePaintedScrollbarLayer : public PaintedScrollbarLayer {
  public:
   static scoped_refptr<FakePaintedScrollbarLayer>
-      Create(bool paint_during_update, bool has_thumb, int scrolling_layer_id);
+      Create(bool paint_during_update,
+             bool has_thumb,
+             int scrolling_layer_id,
+             FakeScrollbar* fake_scrollbar = 0);

[danakj, 2014/02/10 19:17:28]

no default values allowed in chromium. you'll need to update the callsites or
add a second CreateWithScrollbar(). And NULL instead of 0 please.

   int update_count() const { return update_count_; }
   void reset_update_count() { update_count_ = 0; }
 
   virtual bool Update(ResourceUpdateQueue* queue,
                       const OcclusionTracker* occlusion) OVERRIDE;
 
   virtual void PushPropertiesTo(LayerImpl* layer) OVERRIDE;
 
   scoped_ptr<base::AutoReset<bool> > IgnoreSetNeedsCommit();
 
@@ skipping 18 matching lines @@
   virtual ~FakePaintedScrollbarLayer();
 
   int update_count_;
   size_t push_properties_count_;
   FakeScrollbar* fake_scrollbar_;
 };
 
 }  // namespace cc
 
 #endif  // CC_TEST_FAKE_PAINTED_SCROLLBAR_LAYER_H_