static parseCOLR(reader) {
    let colorGamut = null;
    let videoRange = null;
    const data = reader.readBytes(4);
    let colorType = '';
    colorType += String.fromCharCode(data[0]);
    colorType += String.fromCharCode(data[1]);
    colorType += String.fromCharCode(data[2]);
    colorType += String.fromCharCode(data[3]);
    if (colorType === 'nclx') {
      const colorPrimaries = reader.readUint16();
      switch (colorPrimaries) {
        case 1:
        case 5:
        case 6:
        case 7:
          colorGamut = 'srgb';
          break;
        case 9:
          colorGamut = 'rec2020';
          break;
        case 11:
        case 12:
          colorGamut = 'p3';
          break;
      }
      const transferCharacteristics = reader.readUint16();
      reader.readUint16(); // matrix_coefficients
      switch (transferCharacteristics) {
        case 1:
        case 6:
        case 13:
        case 14:
        case 15:
          videoRange = 'SDR';
          break;
        case 16:
          videoRange = 'PQ';
          break;
        case 18:
          videoRange = 'HLG';
          break;
      }
    }
    return {
      colorGamut,
      videoRange,
    };
  }
Parses a COLR box.
@param {!shaka.util.DataViewReader} reader
@return {!shaka.util.ParsedCOLRBox}