Nope, you're thinking of GWT. Relatively few Google products actually use GWT; the bulk of them are on Closure. GMail's client (and Google+, and Docs, and Search) all use Javascript-compiled-to-Javascript for the client side.
I've always wondered why GWT isn't much more popular (at least, for google properties). I know of a half dozen apps written in GWT by google. The rest is probably in closure (or something else).
Perhaps they still haven't solved the SEO problem of GWT internally, and so only things that don't need SEO-features like control panels, dashboards (but ironically, the google groups forums too) are in GWT.
GWT on AppEngine (which it has great integration for) has a ten second startup time when not loaded, and on the free tier they unload it when not in use, so that's not the greatest.
I used GWT for a while and it would be great for enterprise and large teams. The static typing which I usually love/insist on though, does seem pretty cumbersome for something as simple as a web page. I've switched to scala play for the back end and lots of tiny angular 'apps' on the front, and it's so much faster to develop for.
a lot of people who i've spoken to have the same impression of GWT (that it's slow, and not "webby"). I suspect it's because it has the same UI library model as java Swing, and that has the reputation of being slow (thru no fault of java to be honest - its usually the programmers who made it slow, when it could've been fast).
http://www.google.com/fonts <-- loads fast for me. In fact, i think GWT apps can do loading in such an optimized way that hand coding js will only beat it if the programmer is very very careful about it.
(ps, i have no affiliation with google, i just don't like mistunderstood tech to suffer…)
