[Sync::USS] Implement PasswordSyncBridge::GetStorageKey()

Bug: 902349
Change-Id: If5d3ff4cfee29561e735af66cca2453a104dba32
Reviewed-on: https://chromium-review.googlesource.com/c/1402444
Reviewed-by: Mikel Astiz <mastiz@chromium.org>
Commit-Queue: Mohamed Amir Yosef <mamir@chromium.org>
Cr-Commit-Position: refs/heads/master@{#621136}
2 files changed