GitLab

There's a collection of extension API methods that have been deprecated
for some time. Restrict these to manifest version 2, so that they are
unused in manifest version 3.

Bug: 987838
Change-Id: I5ec33a29ceb1eade40e1b97f3692164b581715fb
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2441022Reviewed-by: Karan Bhatia <karandeepb@chromium.org>
Commit-Queue: Devlin <rdevlin.cronin@chromium.org>
Cr-Commit-Position: refs/heads/master@{#814859}