This CL is activating the delegate WorkerPool in Chromium.

Must land after:
  https://chromium-review.googlesource.com/c/angle/angle/+/2231708

Related CLs:
1) https://chromium-review.googlesource.com/c/angle/angle/+/2231708
2) https://chromium-review.googlesource.com/c/chromium/src/+/2231864
3) [this CL]

Bug: chromium:1091259
Change-Id: I62c7175fec2846fee014702d8561eeaf48ca93de
Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/2231710
Commit-Queue: Etienne Bergeron <etienneb@chromium.org>
Commit-Queue: Jamie Madill <jmadill@chromium.org>
Reviewed-by: Jamie Madill <jmadill@chromium.org>