Method collapsedCallback

src/base-element.js:997–999

* Called every time an owned AmpElement collapses itself. * See collapse. * @param {!AmpElement} unusedElement Child element that was collapsed.

(unusedElement)

   * @param {!AmpElement} unusedElement Child element that was collapsed.
   */
  collapsedCallback(unusedElement) {
    // Subclasses may override.
  }

  /**
   * Expands the element, resetting its default display value, and notifies its