notifyOfSuppression_() {
    if (this.interactionSuppressed_) {
      goog.dom.classlist.add(goog.dom.getElement('webview'), 'blurred');
      if (!this.isPromptDisplayed_()) {
        this.displayError_('interactionSuppressed');
      }
      setTimeout(function() {
        goog.dom.classlist.remove(goog.dom.getElement('webview'), 'blurred');
      }, 100);  // Remove the blurring transformation after 100ms.
    }
  }
Notifies the user that interaction with the web application was suppressed.
@private