Refactor to adopt OnceCallback in USS ModelTypeStore API

This is a manually generated patch to update a widely used class in USS,
which prevents new datatypes from properly adopting OnceCallback in
their internals.

No behavioral differences.

Bug: 714018
Cq-Include-Trybots: master.tryserver.chromium.mac:ios-simulator-cronet;master.tryserver.chromium.mac:ios-simulator-full-configs
Change-Id: If5c63f0c180e077980a74a9dd60def7b9171def4
Reviewed-on: https://chromium-review.googlesource.com/897865
Reviewed-by: Pavel Yatsuk <pavely@chromium.org>
Reviewed-by: Olivier Robin <olivierrobin@chromium.org>
Reviewed-by: Sean Kau <skau@chromium.org>
Reviewed-by: Marc Treib <treib@chromium.org>
Commit-Queue: Mikel Astiz <mastiz@chromium.org>
Cr-Commit-Position: refs/heads/master@{#534978}
24 files changed