WeakMap exception
        // Invalid value used as weak map key
        list.items = [
          'Responsive Web App boilerplate',
          'Iron Elements and Paper Elements',
          'End-to-end Build Tooling (including Vulcanize)',
          'Unit testing with Web Component Tester',
          'Routing with Page.js',
          'Offline support with the Platinum Service Worker Elements'
        ];

        // Data bindings will stamp out new DOM asynchronously
        // so wait to check for updates
    