code: function(opt_maxPoolSize) {
    /**
     * The max pool size as configured.
     *
     * @private {number}
     */
    this.maxPoolSizeConfigured_ =
        opt_maxPoolSize || ForwardChannelRequestPool.MAX_POOL_SIZE_;
  
    /**
     * The current size limit of the request pool. This limit is meant to be
     * read-only after the channel is fully opened.
     *
     * If SPDY or HTTP2 is enabled, set it to the max pool size, which is also
     * configurable.
     *
     * @private {number}
     */
    this.maxSize_ = ForwardChannelRequestPool.isSpdyOrHttp2Enabled_() ?
        this.maxPoolSizeConfigured_ :
        1;
  
    /**
     * The container for all the pending request objects.
     *
     * @private {Set<ChannelRequest>}
     */
    this.requestPool_ = null;
  
    if (this.maxSize_ > 1) {
      this.requestPool_ = new Set();
    }
  
    /**
     * The single request object when the pool size is limited to one.
     *
     * @private {ChannelRequest}
     */
    this.request_ = null;
  
    /**
     * Saved pending messages when the pool is cancelled.
     *
     * @private {!Array<Wire.QueuedMap>}
     */
    this.pendingMessages_ = [];
  }
docs: This class represents the state of all forward channel requests.
  
  @param {number=} opt_maxPoolSize The maximum pool size.
  
  @struct @constructor @final