scrollView->ScrollByPages(aForward ? 1 : -1);
scrollView->ScrollByPages(0, aForward ? 1 : -1);
PresShell::ScrollPage(PRBool aForward){  nsCOMPtr<nsIViewManager> viewManager;  nsresult result = GetViewManager(getter_AddRefs(viewManager));  if (NS_SUCCEEDED(result) && viewManager)  {    nsIScrollableView *scrollView;    result = viewManager->GetRootScrollableView(&scrollView);    if (NS_SUCCEEDED(result) && scrollView)    {      scrollView->ScrollByPages(aForward ? 1 : -1);    }  }  return result;}