This CL moves JS formatting behind the --js flag for git cl format
due to issue with LayoutTests. It also adds an option to check
javascript for the presubmit canned formatting check.

BUG=567770

Change-Id: I9c080b1136f6ffef9fb1b08d3bfc97ce5b3185dc
Reviewed-on: https://chromium-review.googlesource.com/430526Reviewed-by: Andrii Shyshkalov <tandrii@chromium.org>
Commit-Queue: Christopher Lam <calamity@chromium.org>