Function notifyIfChanged

src/utils/display-observer.js:491–497

* @param {!Array } callbacks * @param {!Element} target * @param {boolean} newDisplay * @param {boolean} oldDisplay

(callbacks, target, newDisplay, oldDisplay)

 * @param {boolean} oldDisplay
 */
function notifyIfChanged(callbacks, target, newDisplay, oldDisplay) {
  if (newDisplay != null && newDisplay !== oldDisplay) {
    for (let i = 0; i < callbacks.length; i++) {
      callCallbackNoInline(callbacks[i], target, newDisplay);
    }
  }
}

/**
 * @param {!ObserverCallbackDef} callback