Change ppapi C++ comment style into C.

ppapi/c/pp_size.h

Index: ppapi/c/pp_size.h
diff --git a/ppapi/c/pp_size.h b/ppapi/c/pp_size.h
index 722af51dd3860aab22f1dda16039643c68f47e98..945a499d40be46f14d89d52a797612cc2214ecef 100644
--- a/ppapi/c/pp_size.h
+++ b/ppapi/c/pp_size.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_SIZE_H_
 #define PPAPI_C_PP_SIZE_H_
 
@@ -33,4 +33,5 @@ PP_INLINE struct PP_Size PP_MakeSize(int32_t w, int32_t h) {
  * @}
  * End addtogroup PP
  */
-#endif  // PPAPI_C_PP_SIZE_H_
+#endif  /* PPAPI_C_PP_SIZE_H_ */
+