Method _getShadowRoot

src/cdk/drag-drop/drop-list-ref.ts:787–794

* Lazily resolves and returns the shadow root of the element. We do this in a function, rather * than saving it in property directly on init, because we want to resolve it as late as possible * in order to ensure that the element has been moved into the shadow DOM. Doing it inside the * con

()

   * constructor might be too early if the element is inside of something like `ngFor` or `ngIf`.
   */
  private _getShadowRoot(): DocumentOrShadowRoot {
    if (!this._cachedShadowRoot) {
      const shadowRoot = _getShadowRoot(this._container);
      this._cachedShadowRoot = shadowRoot || this._document;
    }

    return this._cachedShadowRoot;
  }

  /** Notifies any siblings that may potentially receive the item. */
  private _notifyReceivingSiblings() {