function addPopUp($popUp, removeHandler, autoRemove) {
        autoRemove = autoRemove || false;

        _popUps.push($popUp[0]);
        $popUp.data("PopUpManager-autoRemove", autoRemove);
        $popUp.data("PopUpManager-removeHandler", removeHandler);
    }
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} autoRemove - Specify true to indicate the PopUpManager should
     remove the popup from the _popUps array when the popup is closed. Specify false
     when the popup is always persistant in the _popUps array.