Remove Channel ID from //extensions

Bug: 875053
Change-Id: I74c99dea56ae944d85f66d12924286ac1b0fac3e
Reviewed-on: https://chromium-review.googlesource.com/c/1325945
Commit-Queue: Nick Harper <nharper@chromium.org>
Reviewed-by: Chris Palmer <palmer@chromium.org>
Reviewed-by: Devlin <rdevlin.cronin@chromium.org>
Cr-Commit-Position: refs/heads/master@{#622257}
28 files changed