_messageReceived(message) {
    this._messageCallbacks.forEach((callback) => {
      callback(message);
    });
  }
Inspect a js value or specific DOM node. This usually
    means using the current environment's tools
    to inspect the node in the DOM.

    For example, in chrome, `inspect(node)`
    will open the Elements tab in dev tools
    and highlight the DOM node.
    For functions, it will open the sources tab and goto the definition
    @param {Node|Function} node