Clean up media header include guards

media/cast/test/utility/test_util.h

Index: media/cast/test/utility/test_util.h
diff --git a/media/cast/test/utility/test_util.h b/media/cast/test/utility/test_util.h
index 2b487065abe4fcfdd4221e45bf617569206166db..e1320f228434aca5ae8b0e3b761fcaeb13c310d0 100644
--- a/media/cast/test/utility/test_util.h
+++ b/media/cast/test/utility/test_util.h
@@ -2,8 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-#ifndef MEDIA_CAST_TEST_UTILITY_TEST_UTIL_H
-#define MEDIA_CAST_TEST_UTILITY_TEST_UTIL_H
+#ifndef MEDIA_CAST_TEST_UTILITY_TEST_UTIL_H_
+#define MEDIA_CAST_TEST_UTILITY_TEST_UTIL_H_
 
 #include <stddef.h>
 
@@ -29,4 +29,4 @@ class MeanAndError {
 }  // namespace cast
 }  // namespace media
 
-#endif  // MEDIA_CAST_TEST_UTILITY_TEST_UTIL_H
+#endif  // MEDIA_CAST_TEST_UTILITY_TEST_UTIL_H_