This is hybrid application - works on both 1.x and 2.x - they did remove some unnecessary 1.x-only calls from the application. You can find the examples in mai

This is hybrid application - works on both 1.x and 2.x - they did remove some unnecessary 1.x-only calls from the application. You can find the examples in main polymer documentation - I'd expect that lots of existing elements will be migrated to hybrid - so you will still see the old syntax for backwards compatibility.