GitLab

Follow guidance by reillyg@ in crrev.com/c/2314024 to discourage
clients other than Nearby from using [Sync] methods on adapter.mojom.

Change-Id: Ic71e1330747b240ba3f153ac96f6cbab0f375701
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2347166Reviewed-by: Reilly Grant <reillyg@chromium.org>
Reviewed-by: Daniel Cheng <dcheng@chromium.org>
Commit-Queue: Ryan Hansberry <hansberry@chromium.org>
Cr-Commit-Position: refs/heads/master@{#796902}