static checkSegmentIndexSupport(context, initSegmentReference) {
    const ContentType = shaka.util.ManifestParserUtils.ContentType;

    const contentType = context.representation.contentType;
    const containerType = context.representation.mimeType.split('/')[1];

    if (contentType != ContentType.TEXT && containerType != 'mp4' &&
        containerType != 'webm') {
      shaka.log.error(
          'SegmentBase specifies an unsupported container type.',
          context.representation);
      throw new shaka.util.Error(
          shaka.util.Error.Severity.CRITICAL,
          shaka.util.Error.Category.MANIFEST,
          shaka.util.Error.Code.DASH_UNSUPPORTED_CONTAINER);
    }

    if ((containerType == 'webm') && !initSegmentReference) {
      shaka.log.error(
          'SegmentBase does not contain sufficient segment information:',
          'the SegmentBase uses a WebM container,',
          'but does not contain an Initialization element.',
          context.representation);
      throw new shaka.util.Error(
          shaka.util.Error.Severity.CRITICAL,
          shaka.util.Error.Category.MANIFEST,
          shaka.util.Error.Code.DASH_WEBM_MISSING_INIT);
    }
  }
Check if this type of segment index is supported.  This allows for
immediate errors during parsing, as opposed to an async error from
createSegmentIndex().

@param {shaka.dash.DashParser.Context} context
@param {shaka.media.InitSegmentReference} initSegmentReference