Perf: paper-menu-button costs too much to use (166KB)

[ebidel]

I added paper-menu-button to chromestatus.com and it increases page load by 166KB. We should try to slim that down.

There are a lot of deps. One obvious one is to remove web animations. The polyfill alone is 50kb and should be feature detected + lazy loaded. Better would be to do the transitions on pure css.