MaterialSnackbar = function MaterialSnackbar(element) {
    this.element_ = element;
    this.textElement_ = this.element_.querySelector('.' + this.cssClasses_.MESSAGE);
    this.actionElement_ = this.element_.querySelector('.' + this.cssClasses_.ACTION);
    if (!this.textElement_) {
      throw new Error('There must be a message element for a snackbar.');
    }
    if (!this.actionElement_) {
      throw new Error('There must be an action element for a snackbar.');
    }
    this.active = false;
    this.actionHandler_ = undefined;
    this.message_ = undefined;
    this.actionText_ = undefined;
    this.queuedNotifications_ = [];
    this.setActionHidden_(true);
  }
Class constructor for Snackbar MDL component.
Implements MDL component design pattern defined at:
https://github.com/jasonmayes/mdl-component-design-pattern

@constructor
@param {HTMLElement} element The element that will be upgraded.