Remove UAv2 content flag.

The feature has shipped, so we don't need the content flag any more.

Bug: 959850
Change-Id: I21ff38122377cd66fbb4740187d0877c9fb7e058
TBR: [email protected]
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1873384
Commit-Queue: Mustaq Ahmed <[email protected]>
Reviewed-by: Devlin <[email protected]>
Reviewed-by: Alex Moshchuk <[email protected]>
Reviewed-by: Navid Zolghadr <[email protected]>
Cr-Commit-Position: refs/heads/master@{#710877}
19 files changed