log(msg) {
    let id = this.browser;
    const task = this.manifest[this.currentTask];
    if (task) {
      id += `-${task.id}`;
    }

    this._info(`${id}: ${msg}`);
  }
A debugging tool to log to the terminal while tests are running.
XXX: This isn't currently referenced, but it's useful for debugging so
do not remove it.

@param {string} msg - The message to log, it will be prepended with the
   current PDF ID if there is one.