GitLab

Erase WebAppDatabase::BeginTransaction and WebAppDatabase::CancelTransaction.

The contract "There can be only 1 update at a time" is tracked by
the WebAppSyncBridge::is_in_update_ flag anyway.
Get rid of this redundancy.

Bug: 860583
Change-Id: Ib330014773509c9f2201f8e51eb7eccbde2b1705
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1851626
Commit-Queue: Alexey Baskakov <loyso@chromium.org>
Reviewed-by: Marc Treib <treib@chromium.org>
Cr-Commit-Position: refs/heads/master@{#704955}