Migrate iOS Sync UI unittests to Mock/TestSyncService

...instead of ProfileSyncServiceMock, which is an antipattern.

Bug: 910518
Change-Id: Iffd4da62dff2db9add9e930ef37e983c82525934
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1528184
Reviewed-by: Sylvain Defresne <sdefresne@chromium.org>
Commit-Queue: Marc Treib <treib@chromium.org>
Cr-Commit-Position: refs/heads/master@{#641653}
8 files changed