See [4] for the design doc for this change.

We're moving the patching logic from bot_update to gclient.
This way we can test patches of dependencies that modify their DEPS
files as well, for example when ANGLE uploads a patch that modifies
DEPS files to be tested by a Chromium trybot.

Chromium Linux CQ and Angle trybots are already running this way
(see [1] and [2]) and a PSA has already been sent [3]

[1] https://chromium.googlesource.com/chromium/src/+/master/infra/config/global/cr-buildbucket.cfg#214
[2] https://chromium.googlesource.com/angle/angle/+/infra/config/cr-buildbucket.cfg#105
[3] https://groups.google.com/a/google.com/forum/#!topic/chrome-infra/FVHN2kdUX4I
[4] https://docs.google.com/document/d/1GSTw4ysm5AYjNR6vMA7NJUxLK2VN9IpOEp_v0u-wyOE/edit?ts=5ad78165#

Bug: 643346
Change-Id: Ic9a9dcfae86aca730d35fbb26c26b21135e05bf3
Recipe-Nontrivial-Roll: skia
Recipe-Nontrivial-Roll: infra
Recipe-Nontrivial-Roll: build_limited_scripts_slave
Recipe-Nontrivial-Roll: skiabuildbot
Recipe-Nontrivial-Roll: build
Recipe-Nontrivial-Roll: release_scripts
Reviewed-on: https://chromium-review.googlesource.com/1014356
Commit-Queue: Edward Lesmes <ehmaldonado@chromium.org>
Reviewed-by: Aaron Gable <agable@chromium.org>