getBuffered_(contentType) {
    if (this.reloadingMediaSource_ || this.usingRemotePlayback_) {
      return null;
    }
    try {
      return this.sourceBuffers_.get(contentType).buffered;
    } catch (exception) {
      if (this.sourceBuffers_.has(contentType)) {
        // Note: previous MediaSource errors may cause access to |buffered| to
        // throw.
        shaka.log.error('failed to get buffered range for ' + contentType,
            exception);
      }
      return null;
    }
  }
@param {shaka.util.ManifestParserUtils.ContentType} contentType
@return {TimeRanges} The buffered ranges for the given content type, or
  null if the buffered ranges could not be obtained.
@private