Method waitForShadowRoot

testing/helpers/service.js:275–288

* @param {string} hostSelector * @param {number=} timeout * @return {!Promise}

(hostSelectorOrElement, timeout = 10000)

   * @return {!Promise}
   */
  waitForShadowRoot(hostSelectorOrElement, timeout = 10000) {
    const element = this.querySelectorOrElement(hostSelectorOrElement);
    if (!element) {
      throw new Error(
        `BrowserController query failed: ${hostSelectorOrElement}`
      );
    }
    return poll(
      `"${hostSelectorOrElement}" to host shadow doc`,
      () => !!element.shadowRoot,
      /* onError */ undefined,
      timeout
    );
  }

  /**
   * @param {string} selector