[Background Fetch] Cleanup fetch data on browser startup.

A browser might shutdown, for example, when a request moves to the
active state, but before we delete the pending entry.
This CL modifes the initialization DatabaseTask to delete such

Change-Id: Icefcac3789d299c83bbda2b7b1dc117ca4e1a5e0
Reviewed-on: https://chromium-review.googlesource.com/1140164
Commit-Queue: Rayan Kanso <rayankans@chromium.org>
Reviewed-by: Peter Beverloo <peter@chromium.org>
Cr-Commit-Position: refs/heads/master@{#576169}
1 file changed