DevServer-side panic message needs to textContent- any messages it serves up or the any error messages that include HTML will get parsed.
This patch introduces extras and configs

Extras: the place where we will move non-core features, like cc/,
as well as all the importers.

Configs: we ship trace-viewer to a number of end products, from about:tracing
which contains everything we've got, to systrace which has just linux-tracing
related pieces, to adb_profile_chrome whose needs are actually varying. A ton
of fragile pieces of glue have cropped up that make sure each of these delivery
points have the right modules added in. Thats crazy. Lets call these configs
and make them a thing.