Base64PbStreamParser = function() {
  /**
   * The current error message, if any.
   * @private {?string}
   */
  this.errorMessage_ = null;

  /**
   * The current position in the streamed data.
   * @private {number}
   */
  this.streamPos_ = 0;

  /**
   * Base64 stream decoder
   * @private @const {!Base64StreamDecoder}
   */
  this.base64Decoder_ = new Base64StreamDecoder();

  /**
   * Protobuf raw bytes stream parser
   * @private @const
   */
  this.pbParser_ = new PbStreamParser();
}
The default base64-encoded Protobuf stream parser.

@constructor
@struct
@implements {StreamParser}
@final