bool
txXPathTreeWalker::moveToNextSibling()
{
    if (!mPosition.isContent()) {
        return false;
    }

    return moveToSibling(1);
}
bool
txXPathTreeWalker::moveToPreviousSibling()
{
    if (!mPosition.isContent()) {
        return false;
    }

    return moveToSibling(-1);
}
PRBool
txXPathTreeWalker::moveToNextSibling()
{
    if (!mPosition.isContent()) {
        return PR_FALSE;
    }

    return moveToSibling(1);
}