Change ppapi C++ comment style into C.

ppapi/c/ppb_instance.h

Index: ppapi/c/ppb_instance.h
diff --git a/ppapi/c/ppb_instance.h b/ppapi/c/ppb_instance.h
index 6a3588f36f72f199c5432f3fead2133a3a676030..48d47a83642a931d294e4094073721112f562dd5 100644
--- a/ppapi/c/ppb_instance.h
+++ b/ppapi/c/ppb_instance.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_PPB_INSTANCE_H_
 #define PPAPI_C_PPB_INSTANCE_H_
 
@@ -88,4 +88,5 @@ struct PPB_Instance {
  * @}
  * End addtogroup PPB
  */
-#endif  // PPAPI_C_PPB_INSTANCE_H_
+#endif  /* PPAPI_C_PPB_INSTANCE_H_ */
+