legacy/$dom.legacy.js
function _isDescendant(elm, ancestor)
    {
        while ((elm = elm.parentNode) && elm != ancestor) { }
        return elm !== null;
    }
function _isDescendant(elm, ancestor)
    {
        while ((elm = elm.parentNode) && elm != ancestor) { }
        return elm !== null;
    }
function _isDescendant ( elm , ancestor ) { while ( ( elm = elm . parentNode ) && elm != ancestor ) { } return elm !== null ; }
determines if the passed element is a descentand of anthor element
determines if the passed element is a descentand of anthor element