[AF] Encode64 the account hash for the Wallet Sync Transport opt-in.

Bug: 914935
Change-Id: I40c9f26a39db803d961f227e4dd8ec06ce3b2b6d
Reviewed-on: https://chromium-review.googlesource.com/c/1376810
Reviewed-by: David Benjamin <davidben@chromium.org>
Commit-Queue: Sebastien Seguin-Gagnon <sebsg@chromium.org>
Cr-Commit-Position: refs/heads/master@{#616476}
1 file changed