cc: For cc pixel test, create data url for pngs and print bounding rect.

cc/test/pixel_test_utils.h

Index: cc/test/pixel_test_utils.h
diff --git a/cc/test/pixel_test_utils.h b/cc/test/pixel_test_utils.h
index e581e9557219204373cd43b6346a08bc8929f1cc..d8ff7fdeb293961646f5d723eecf75a5540b5b6a 100644
--- a/cc/test/pixel_test_utils.h
+++ b/cc/test/pixel_test_utils.h
@@ -21,6 +21,8 @@ bool WritePNGFile(const SkBitmap& bitmap, const base::FilePath& file_path,
 // should have been encoded using |gfx::PNGCodec::Encode|.
 bool ReadPNGFile(const base::FilePath& file_path, SkBitmap* bitmap);
 
+std::string GetPNGDataUrl(const SkBitmap& bitmap);
+
 // Compares with a PNG file on disk using the given PixelComparator, and returns
 // true if the comparator returns a match. |ref_img_path| is absolute.
 bool MatchesPNGFile(const SkBitmap& gen_bmp,