function addPopUp($popUp, removeHandler, autoAddRemove) {
        autoAddRemove = autoAddRemove || false;
        
        _popUps.push($popUp[0]);
        $popUp.data("PopUpManager-autoAddRemove", autoAddRemove);
        $popUp.data("PopUpManager-removeHandler", removeHandler);
        
        if (autoAddRemove) {
            $(window.document.body).append($popUp);
        }
    }
Add Esc key handling for a popup DOM element.

@param {!jQuery} $popUp jQuery object for the DOM element pop-up
@param {function} removeHandler Pop-up specific remove (e.g. display:none or DOM removal)
@param {?Boolean} autoAddRemove - Specify true to indicate the PopUpManager should 
     add/remove the popup from the DOM when the popup is open/closed. Specify false
     when the popup is either always persistant in the DOM or the add/remove is handled 
     external to the PopupManager