Change ppapi C++ comment style into C.

ppapi/c/dev/ppp_graphics_3d_dev.h

Index: ppapi/c/dev/ppp_graphics_3d_dev.h
diff --git a/ppapi/c/dev/ppp_graphics_3d_dev.h b/ppapi/c/dev/ppp_graphics_3d_dev.h
index ac1de8d33ee71e2f38a4bad3983ff94ffa636087..ae9b2e196f08f0be47a87d0787d19a5cfa392a2c 100644
--- a/ppapi/c/dev/ppp_graphics_3d_dev.h
+++ b/ppapi/c/dev/ppp_graphics_3d_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_GRAPHICS_3D_DEV_H_
 #define PPAPI_C_DEV_PPP_GRAPHICS_3D_DEV_H_
 
@@ -14,5 +14,5 @@ struct PPP_Graphics3D_Dev {
   void (*Graphics3DContextLost)(PP_Instance instance);
 };
 
-#endif  // PPAPI_C_DEV_PPP_GRAPHICS_3D_DEV_H_
+#endif  /* PPAPI_C_DEV_PPP_GRAPHICS_3D_DEV_H_ */