handleError_(error) {
    if (error.code != StatusCode.OK) {
      this.sendErrorCallbacks_(new RpcError(
          error.code, decodeURIComponent(error.message || ''), error.metadata));
    }
    this.sendStatusCallbacks_(/** @type {!Status} */ ({
      code: error.code,
      details: decodeURIComponent(error.message || ''),
      metadata: error.metadata
    }));
  }
A central place to handle errors

@private
@param {!RpcError} error The error object