static createStyledCue(startTime, endTime, underline,
      italics, txtColor, bgColor) {
    const cue = new shaka.text.Cue(startTime, endTime, /* payload= */ '');
    if (underline) {
      cue.textDecoration.push(shaka.text.Cue.textDecoration.UNDERLINE);
    }
    if (italics) {
      cue.fontStyle = shaka.text.Cue.fontStyle.ITALIC;
    }
    cue.color = txtColor;
    cue.backgroundColor = bgColor;
    return cue;
  }
@param {number} startTime
@param {number} endTime
@param {boolean} underline
@param {boolean} italics
@param {string} txtColor
@param {string} bgColor
@return {!shaka.text.Cue}