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

ppapi/proxy/resource_creation_proxy.cc

Index: ppapi/proxy/resource_creation_proxy.cc
===================================================================
--- ppapi/proxy/resource_creation_proxy.cc	(revision 95420)
+++ ppapi/proxy/resource_creation_proxy.cc	(working copy)
@@ -263,11 +263,17 @@
 }
 
 PP_Resource ResourceCreationProxy::CreateScrollbar(PP_Instance instance,
+                                                   PP_Resource scrollbar_group,
                                                    PP_Bool vertical) {
   NOTIMPLEMENTED();  // Not proxied yet.
   return 0;
 }
 
+PP_Resource ResourceCreationProxy::CreateScrollbarGroup(PP_Instance instance) {
+  NOTIMPLEMENTED();  // Not proxied yet.
+  return 0;
+}
+
 PP_Resource ResourceCreationProxy::CreateSurface3D(
     PP_Instance instance,
     PP_Config3D_Dev config,