Fixed rounding issue on scrollbar rasterization.

cc/test/fake_scrollbar.h

Index: cc/test/fake_scrollbar.h
diff --git a/cc/test/fake_scrollbar.h b/cc/test/fake_scrollbar.h
index 41152f6ec9f833c9fe5f593b8a0ec571534bc67a..5e2c23e0283cfc6010a2a5561316e92fa72c3bc8 100644
--- a/cc/test/fake_scrollbar.h
+++ b/cc/test/fake_scrollbar.h
@@ -36,6 +36,7 @@ class FakeScrollbar : public Scrollbar {
       thumb_thickness_ = thumb_thickness;
   }
   void set_thumb_length(int thumb_length) { thumb_length_ = thumb_length; }
+  SkColor get_color() const { return SK_ColorBLACK | fill_color_; }
 
  private:
   bool paint_;