With this, `fetch chromium` manages to client src.git and all
dependencies in DEPS (and then dies in runhooks).

Bug: 1103236
Change-Id: I0e26b78f1c552aa23eaa6c43b61f3c6809a3ada1
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/tools/depot_tools/+/2287751
Auto-Submit: Nico Weber <thakis@chromium.org>
Reviewed-by: Mark Mentovai <mark@chromium.org>
Reviewed-by: Dirk Pranke <dpranke@google.com>
Reviewed-by: Edward Lesmes <ehmaldonado@chromium.org>
Commit-Queue: Nico Weber <thakis@chromium.org>