[AF] Add test for the Wallet Sync Transport opt-in pref serialization

Bug: 914935
Change-Id: I52dde692e3f803cf5923090541371bec726667d5
Reviewed-on: https://chromium-review.googlesource.com/c/1378231
Reviewed-by: Tommy Martino <tmartino@chromium.org>
Commit-Queue: Sebastien Seguin-Gagnon <sebsg@chromium.org>
Cr-Commit-Position: refs/heads/master@{#616749}
1 file changed