Change ppapi C++ comment style into C.

ppapi/c/dev/ppp_widget_dev.h

Index: ppapi/c/dev/ppp_widget_dev.h
diff --git a/ppapi/c/dev/ppp_widget_dev.h b/ppapi/c/dev/ppp_widget_dev.h
index 27c7794b7d6eb4e008ee3c2f3e7496e7dd1e47ac..41855511942530834c883ca163500a40cca70834 100644
--- a/ppapi/c/dev/ppp_widget_dev.h
+++ b/ppapi/c/dev/ppp_widget_dev.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_DEV_PPP_WIDGET_DEV_H_
 #define PPAPI_C_DEV_PPP_WIDGET_DEV_H_
 
@@ -19,4 +19,5 @@ struct PPP_Widget_Dev {
                      const struct PP_Rect* dirty_rect);
 };
 
-#endif  // PPAPI_C_DEV_PPP_WIDGET_DEV_H_
+#endif  /* PPAPI_C_DEV_PPP_WIDGET_DEV_H_ */
+