Fixed rounding issue on scrollbar rasterization.

cc/layers/painted_scrollbar_layer.h

Index: cc/layers/painted_scrollbar_layer.h
diff --git a/cc/layers/painted_scrollbar_layer.h b/cc/layers/painted_scrollbar_layer.h
index 4799bfb3fa14fd6504e6a06f02c6d306d619922d..3a959b84979e2a4bdac56c5e19c5a03e76fda15a 100644
--- a/cc/layers/painted_scrollbar_layer.h
+++ b/cc/layers/painted_scrollbar_layer.h
@@ -77,7 +77,8 @@ class CC_EXPORT PaintedScrollbarLayer : public ScrollbarLayerInterface,
   int MaxTextureSize();
   float ClampScaleToMaxTextureSize(float scale);
 
-  UIResourceBitmap RasterizeScrollbarPart(const gfx::Rect& rect,
+  UIResourceBitmap RasterizeScrollbarPart(const gfx::Rect& layer_rect,
+                                          const gfx::Rect& rect,
                                           ScrollbarPart part);
 
   scoped_ptr<Scrollbar> scrollbar_;