ronResizableBehavior` behavior to
   * their element definition and listen for the `iron-resize` event on themselves.
   * This event will be fired when they become showing after having been hidden,
   * when they are resized explicitly by another resizable, or when the window has been
   * resized.
   *
   * Note, the `iron-resize` event is non-bubbling.
   *
   * @polymerBehavior Polymer.IronResizableBehavior
   * @demo demo/index.html
   **/
  Polymer.IronResizableBehavior = {
    properties: {
      /**