Pepper and WebKit API change to support a plugin knowing if a scrollbar is an overlay one.

ppapi/c/dev/ppp_scrollbar_dev.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.
  */
 #ifndef PPAPI_C_DEV_PPP_SCROLLBAR_DEV_H_
 #define PPAPI_C_DEV_PPP_SCROLLBAR_DEV_H_
 
+#include "ppapi/c/pp_bool.h"
 #include "ppapi/c/pp_instance.h"
 #include "ppapi/c/pp_resource.h"
 #include "ppapi/c/pp_stdint.h"
 
 // Interface for the plugin to implement when using a scrollbar widget.
-#define PPP_SCROLLBAR_DEV_INTERFACE "PPP_Scrollbar(Dev);0.2"
+#define PPP_SCROLLBAR_DEV_INTERFACE_0_2 "PPP_Scrollbar(Dev);0.2"
+#define PPP_SCROLLBAR_DEV_INTERFACE_0_3 "PPP_Scrollbar(Dev);0.3"
+#define PPP_SCROLLBAR_DEV_INTERFACE PPP_SCROLLBAR_DEV_INTERFACE_0_3
 
 struct PPP_Scrollbar_Dev {
   // Informs the instance that the scrollbar's value has changed.
   void (*ValueChanged)(PP_Instance instance,
                        PP_Resource scrollbar,
                        uint32_t value);
+
+  // Informs the instance that the user has changed the system scrollbar style.
+  void (*OverlayChanged)(PP_Instance instance,
+                         PP_Resource scrollbar,
+                         PP_Bool overlay);
 };
 
 #endif  /* PPAPI_C_DEV_PPP_SCROLLBAR_DEV_H_ */