*parent = mParent; NS_IF_ADDREF(*parent);
if(parent) parent->QueryInterface(NS_GET_IID(nsIWebShell), (void**)&aParent); else aParent = nsnull;
NS_IMETHODIMP nsWebShell::GetParent(nsIDocShellTreeItem** parent){   NS_ENSURE_ARG_POINTER(parent);   *parent = mParent;   NS_IF_ADDREF(*parent);   return NS_OK;}