GitLab

Use PrefRegistrySyncable's new whitelist for delayed pref registration.
(there's a race between ash prefs connecting to chrome and sync init)
Avoids PrefServiceSyncable::AddRegisteredSyncablePreference DCHECKs.

See the bug and earlier patch sets for debug code to trigger the race:
1) Build chromeos=1 on linux desktop with this patch applied
2) Run chrome --user-data-dir=/tmp/foo --login-manager
3) Go through setup, sign in to an existing account
4) Launch chrome again, sign in quickly, wait ~10s for a DCHECK

Bug: 788918
Change-Id: Ib505194900b34154b3896373b93c951a6eeb8715
Reviewed-on: https://chromium-review.googlesource.com/1012788Reviewed-by: James Cook <jamescook@chromium.org>
Commit-Queue: Michael Wasserman <msw@chromium.org>
Cr-Commit-Position: refs/heads/master@{#563037}