Change ppapi C++ comment style into C.

ppapi/c/ppp_instance.h

-// 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_PPP_INSTANCE_H_
 #define PPAPI_C_PPP_INSTANCE_H_
 
 #include "ppapi/c/pp_bool.h"
 #include "ppapi/c/pp_instance.h"
 #include "ppapi/c/pp_rect.h"
 #include "ppapi/c/pp_resource.h"
 
 struct PP_InputEvent;
 struct PP_Var;
@@ skipping 109 matching lines @@
    * The returned PP_Var should have a reference added for the caller, which
    * will be responsible for Release()ing that reference.
    */
   struct PP_Var (*GetInstanceObject)(PP_Instance instance);
 };
 
 /**
  * @}
  * End addtogroup PPP
  */
-#endif  // PPAPI_C_PPP_INSTANCE_H_
+#endif  /* PPAPI_C_PPP_INSTANCE_H_ */
+