function* openSyntheticWindowEnvironment({ $id: windowId = generateDefaultId(), location, bounds, scrollPosition }: SyntheticWindow, browserId: string) {

  let main: SEnvWindowInterface;
  const documentId = generateDefaultId();
  const fetch = yield getFetch();
  const { apiHost }: SyntheticBrowserRootState = yield select();

  let currentWindow: SEnvWindowInterface;

  const reloadChan = yield eventChannel((emit) => {

    const reload = (bounds?: Bounds) => {
      if (currentWindow) {
        currentWindow.dispose();
      }
      const SEnvWindow = getSEnvWindowClass({ 
        console: getSEnvWindowConsole(), 
        fetch, 
        reload: () => reload(),
        getProxyUrl: (url: string) => {
          return apiHost && url.substr(0, 5) !== "data:" && url.indexOf(window.location.host) === -1 ? apiHost + "/proxy/" + encodeURIComponent(url) : url;
        },
        createRenderer: (window: SEnvWindowInterface) => {
          return window.top === window ? new SyntheticMirrorRenderer(window) : new SyntheticDOMRenderer(window, document)
        }
      });
      const window = currentWindow = new SEnvWindow(location, browserId);
  
      // ick. Better to use seed function instead to generate UIDs <- TODO.
      window.$id = windowId;
      window.document.$id = documentId;
  
      if (bounds) {
        window.moveTo(bounds.left, bounds.top);
        if (bounds.right) {
          window.resizeTo(bounds.right - bounds.left, bounds.bottom - bounds.top);
        }
      }

      emit(window);

      return window;
    };

    reload(bounds);

    return () => { };
  });

  yield spawn(function*() {
    while(true) {
      yield watchWindowExternalResourceUris(currentWindow, () => currentWindow.location.reload());
      currentWindow.$load();
      const isNew = !getSyntheticWindow(yield select(), currentWindow.$id);
      yield put(syntheticWindowOpened(currentWindow, null, isNew));
      yield take(reloadChan);
    }
  });
}

export const mutateSourceContentRequest = (content: string, contentType: string, mutation: Mutation<any>): MutateSourceContentRequest<any> => ({
  content,
  mutation,
  contentType,
  $id: generateDefaultId(),
  type: EDIT_SOURCE_CONTENT,
});

    constructor() {
      super();
      this.$id = generateDefaultId();
      this.childNodes = this.childNodesArray = new SEnvNodeList();

      // called specifically for elements
      if (this._constructed) {
        throw new Error(`Cannot call constructor twice.`);
      }
      this._constructed = true;
      this.addEventListener(SEnvMutationEvent.MUTATION, this._onMutation.bind(this));
    }

 constructor() {
   this._$id = generateDefaultId();
 }