Change ppapi C++ comment style into C.

ppapi/c/dev/ppb_file_ref_dev.h

Index: ppapi/c/dev/ppb_file_ref_dev.h
diff --git a/ppapi/c/dev/ppb_file_ref_dev.h b/ppapi/c/dev/ppb_file_ref_dev.h
index e56fa1cb7ad765153427d8e480f8a409bb13fe4f..0f74a7c7e623fe416151738d5f64f2deb1ce0f0f 100644
--- a/ppapi/c/dev/ppb_file_ref_dev.h
+++ b/ppapi/c/dev/ppb_file_ref_dev.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_DEV_PPB_FILE_REF_DEV_H_
 #define PPAPI_C_DEV_PPB_FILE_REF_DEV_H_
 
@@ -80,4 +80,5 @@ struct PPB_FileRef_Dev {
                     struct PP_CompletionCallback callback);
 };
 
-#endif  // PPAPI_C_DEV_PPB_FILE_REF_DEV_H_
+#endif  /* PPAPI_C_DEV_PPB_FILE_REF_DEV_H_ */
+