Method init_

src/service/hidden-observer-impl.js:62–75

* Initializes the mutation observer and observable.

()

   * Initializes the mutation observer and observable.
   */
  init_() {
    if (this.mutationObserver_) {
      return;
    }
    this.observable_ = new Observable();

    const mo = new this.win_.MutationObserver((mutations) => {
      if (mutations) {
        this.observable_.fire(mutations);
      }
    });
    this.mutationObserver_ = mo;
    mo.observe(this.root_, OBSERVER_OPTIONS);
  }

  /**
   * Cleans up the all the mutation observer once the last listener stops