Change ppapi C++ comment style into C.

ppapi/c/ppb_core.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_PPB_CORE_H_
 #define PPAPI_C_PPB_CORE_H_
 
 #include "ppapi/c/pp_bool.h"
 #include "ppapi/c/pp_resource.h"
 #include "ppapi/c/pp_stdint.h"
 #include "ppapi/c/pp_time.h"
 #include "ppapi/c/pp_var.h"
 
 struct PP_CompletionCallback;
@@ skipping 68 matching lines @@
    * This is useful for implementing sanity checks, and deciding if dispatching
    * via CallOnMainThread() is required.
    */
   PP_Bool (*IsMainThread)();
 };
 
 /**
  * @}
  * End addtogroup PPB
  */
-#endif  // PPAPI_C_DEV_PPB_CORE_DEV_H_
+#endif  /* PPAPI_C_DEV_PPB_CORE_DEV_H_ */
+