Add --autoroll option which expects an existing git commit by the
autoroller, which updates chromium_revision.
roll_chromium_deps.py then updates other ANGLE dependencies to the
revision of their Chromium counterparts and amends autoroller's commit.

Bug: skia:10572
Change-Id: Iddb9296bd1470f4a2113563c5ed3a1c27e16f128
Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/2363212
Commit-Queue: Yuly Novikov <ynovikov@chromium.org>
Reviewed-by: Jamie Madill <jmadill@chromium.org>