Finally remove all deprecated BrowserThreads and cleanup remaining dependencies.

This is the final piece in the attempt to reland
https://chromium-review.googlesource.com/c/chromium/src/+/705775

Bug: 804345
Change-Id: I240576ae186886ae9b76c50a7920aed37b3a4ff1

TBR=avi@chromium.org, jam@chromium.org (fwd'ing from https://chromium-review.googlesource.com/c/chromium/src/+/705775)

Change-Id: I240576ae186886ae9b76c50a7920aed37b3a4ff1
Reviewed-on: https://chromium-review.googlesource.com/890263
Commit-Queue: Gabriel Charette <gab@chromium.org>
Reviewed-by: Alexei Svitkine <asvitkine@chromium.org>
Reviewed-by: Dirk Pranke <dpranke@chromium.org>
Cr-Commit-Position: refs/heads/master@{#533640}
14 files changed