These two checks are lifted directly from the Chromium code base. Also
adds a presubmit check for a patch description. Also adds some checks
to the "on commit" function so "git cl presubmit" can work.

Also reformats the style of the presubmit script a bit to match the
patterns in the Chromium presubmit.

Bug: angleproject:2626
Bug: angleproject:3054
Change-Id: Iff29b8856cf9eb9531e893cd0b0d80c0834b7676
Reviewed-on: https://chromium-review.googlesource.com/c/1403255Reviewed-by: Shahbaz Youssefi <syoussefi@chromium.org>
Commit-Queue: Jamie Madill <jmadill@chromium.org>