createChannel_() {
    if (this.channel_) {
      this.channel_.dispose();
    }
    this.channel_ = new CrossPageChannel(this.outerFrameCfg_);
    this.channel_.registerService('echo', goog.bind(this.echoHandler_, this));
    this.channel_.registerService(
        'response', goog.bind(this.responseHandler_, this));

    return this.channel_.name;
  }
Creates an outer frame channel object.
@return {string}
@private
@suppress {checkTypes} suppression added to enable type checking