TextArea的滚动条看不到了，可能与height有关

TextArea的滚动条看不到了，可能与height有关，Adobe规定height低于40就不让见了:

/**
     *  Specifies whether the horizontal scroll bar is
     *  always on (<code>ScrollPolicy.ON</code>),
     *  always off (<code>ScrollPolicy.OFF</code>),
     *  or turns on when needed (<code>ScrollPolicy.AUTO</code>).
     *
     *  @default ScrollPolicy.AUTO
     * 
     */
    override public function get horizontalScrollPolicy():String
    {
        return height <= 40 ? ScrollPolicy.OFF :  _horizontalScrollPolicy;
    }