Change ppapi C++ comment style into C.

ppapi/c/dev/ppb_graphics_3d_dev.h

Index: ppapi/c/dev/ppb_graphics_3d_dev.h
diff --git a/ppapi/c/dev/ppb_graphics_3d_dev.h b/ppapi/c/dev/ppb_graphics_3d_dev.h
index 7bd739be0a83cdad7ea9e1e4bdf57e80089b2e4c..6229249459fcc2c78f1619da219aa5c4c9ad1198 100644
--- a/ppapi/c/dev/ppb_graphics_3d_dev.h
+++ b/ppapi/c/dev/ppb_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_PPB_GRAPHICS_3D_DEV_H_
 #define PPAPI_C_DEV_PPB_GRAPHICS_3D_DEV_H_
 
@@ -101,4 +101,5 @@ struct PPB_Graphics3D_Dev {
   uint32_t (*GetError)();
 };
 
-#endif  // PPAPI_C_DEV_PPB_GRAPHICS_3D_DEV_H_
+#endif  /* PPAPI_C_DEV_PPB_GRAPHICS_3D_DEV_H_ */
+