Change ppapi C++ comment style into C.

ppapi/c/pp_errors.h

Index: ppapi/c/pp_errors.h
diff --git a/ppapi/c/pp_errors.h b/ppapi/c/pp_errors.h
index a5ab5d1f77dddc554fe9afa533fde8f06ceb0919..5d2e13a2a51a3703d259b9a662ac5e53d845f659 100644
--- a/ppapi/c/pp_errors.h
+++ b/ppapi/c/pp_errors.h
@@ -1,7 +1,7 @@
-// Copyright (c) 2010 The Chromium Authors. All rights reserved.
-// Use of this source code is governed by a BSD-style license that can be
-// found in the LICENSE file.
-
+/* Copyright (c) 2010 The Chromium Authors. All rights reserved.
+ * Use of this source code is governed by a BSD-style license that can be
+ * found in the LICENSE file.
+ */
 #ifndef PPAPI_C_PP_ERRORS_H_
 #define PPAPI_C_PP_ERRORS_H_
 
@@ -79,4 +79,5 @@ enum {
  * End of addtogroup PP
  */
 
-#endif  // PPAPI_C_PP_ERRORS_H_
+#endif  /* PPAPI_C_PP_ERRORS_H_ */
+