function triggerTimingFunctionEditorKey(opts) {
                    makeTimingFuncUI(opts.func, opts.callback);
                    var $item = $(timingFuncEditor[opts.item]);
                    $item.focus();
                    $item.trigger(makeKeyEvent(opts));
                }
Create a timing function editor and trigger a key event on it.
@param {object} opts The parameters to test:
    func: The initial timing function
    item: The (string) name of the member of BezierCurveEditor
         that references the element to test.
    key: The KeyEvent key code to simulate.
    shift: Optional boolean specifying whether to simulate the shift
         key being down (default false).
    expected: The expected array of values for _cubicBezierCoords.