Fixed rounding issue on scrollbar rasterization.

cc/test/fake_scrollbar.cc

Index: cc/test/fake_scrollbar.cc
diff --git a/cc/test/fake_scrollbar.cc b/cc/test/fake_scrollbar.cc
index 7285660f17016fc5be6e56070a40a817d7dfe0e2..f500a2a2861e99b17f2c832f1f89db7cd7af2a41 100644
--- a/cc/test/fake_scrollbar.cc
+++ b/cc/test/fake_scrollbar.cc
@@ -5,6 +5,7 @@
 #include "cc/test/fake_scrollbar.h"
 
 #include "third_party/skia/include/core/SkCanvas.h"
+#include "ui/gfx/skia_util.h"
 
 namespace cc {
 
@@ -62,7 +63,16 @@ void FakeScrollbar::PaintPart(SkCanvas* canvas,
 
   // Fill the scrollbar with a different color each time.
   fill_color_++;
-  canvas->clear(SK_ColorBLACK | fill_color_);
+
+  if (part == TRACK) {
+    SkPaint paint;
+    paint.setAntiAlias(false);
+    paint.setColor(get_color());
+    paint.setStyle(SkPaint::kFill_Style);
+    canvas->drawRect(RectToSkRect(TrackRect()), paint);
+  } else {
+    canvas->clear(get_color());
+  }
 }
 
 }  // namespace cc