PSA: You can now try JavaScript changes via Closure Compiler

[Dan Beam]

Hey all,

If you don't write JavaScript in Chrome, you can stop reading now.

As of https://codereview.chromium.org/1923783002/, CLs touching:

 - chrome/browser/resources/
 - ui/webui/resources/

will automatically add the line:

  CQ_INCLUDE_TRYBOTS=tryserver.chromium.linux:closure_compilation

to your CL description and block your CQ on JavaScript typechecking issues (doc update coming).

If you work on typechecked JavaScript outside these directories, you can add ^ that line to your CL description or run this command:

  $ git cl try -b closure_compilation

or "Choose trybots" on your CL ("closure_compilation" in the "tryserver.chromium.linux" section) to try your change once.

Closure try bots have been a long time coming.  We've been running closure on a subset of Chrome JavaScript via an FYI bot for 2 years now with high dependency, fast cycles times, and minimal issues.  Hopefully Closure makes it to the main waterfall soon, ;).

-- Dan