parseTilesLayout_(tilesLayout) {
    if (!tilesLayout) {
      return null;
    }
    // This expression is used to detect one or more numbers (0-9) followed
    // by an x and after one or more numbers (0-9)
    const match = /(\d+)x(\d+)/.exec(tilesLayout);
    if (!match) {
      shaka.log.warning('Tiles layout does not contain a valid format ' +
          ' (columns x rows)');
      return null;
    }
    const columns = parseInt(match[1], 10);
    const rows = parseInt(match[2], 10);
    return {columns, rows};
  }
Parses a tiles layout.

@param {string|undefined} tilesLayout
@return {?{
  columns: number,
  rows: number
}}
@private