[Mfill Android] Always close accessory on filling

Before this change, the accessory would pass a callback to the renderer
that is called with either success or failure state on completion.
Since a failure has become very unlikely and we don't actually gain any
information even if it should fail, the code can be simplified a lot by
dropping it and closing the accessory directly (which this CL does).
This is also a solid general case for all fallback sheets and makes the
closing consistent across all of them (see linked bug).

Bug: 962548
Change-Id: I4c173f37a6cbb6513f0c0218494ff9aeb5156836
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1703404
Reviewed-by: Vadym Doroshenko <dvadym@chromium.org>
Reviewed-by: Mike West <mkwst@chromium.org>
Commit-Queue: Friedrich [CET] <fhorschig@chromium.org>
Cr-Commit-Position: refs/heads/master@{#678213}
20 files changed