cc: Fix readback from non-root layers.

cc/test/pixel_test.h

Index: cc/test/pixel_test.h
diff --git a/cc/test/pixel_test.h b/cc/test/pixel_test.h
index 6fb8135f07f67439979e593547e5d7e10290ee85..148ecf939ecaadf28a94fb74ec3f4ff308ccdfc5 100644
--- a/cc/test/pixel_test.h
+++ b/cc/test/pixel_test.h
@@ -27,6 +27,11 @@ class PixelTest : public testing::Test {
                     const base::FilePath& ref_file,
                     const PixelComparator& comparator);
 
+  bool RunPixelTestWithReadbackTarget(RenderPassList* pass_list,
+                                      RenderPass* target,
+                                      const base::FilePath& ref_file,
+                                      const PixelComparator& comparator);
+
   gfx::Size device_viewport_size_;
   scoped_ptr<OutputSurface> output_surface_;
   scoped_ptr<ResourceProvider> resource_provider_;