Change ppapi C++ comment style into C.

ppapi/c/pp_time.h

Index: ppapi/c/pp_time.h
diff --git a/ppapi/c/pp_time.h b/ppapi/c/pp_time.h
index 330a16c396fede1cdfc96bb6f1d95c714a72b46c..1672531a3c7edfa0cca79b0a354e7c449bd2bf53 100644
--- a/ppapi/c/pp_time.h
+++ b/ppapi/c/pp_time.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_TIME_H_
 #define PPAPI_C_PP_TIME_H_
 
@@ -39,4 +39,5 @@ PP_COMPILE_ASSERT_SIZE_IN_BYTES(PP_TimeTicks, 8);
  * @}
  * End addtogroup PP
  */
-#endif  // PPAPI_C_PP_TIME_H_
+#endif  /* PPAPI_C_PP_TIME_H_ */
+