Re-enable OAuth2TokenService tests

Try to re-enable previously flaky tests. This will be followed up by
the removal of OAuth2TokenService.GetAccessTokenWithTimeout which is an
unused API.

Some modifications were required to run a part of the test in the
UIThread (assertions added after the tests were disabled).

Bug: 960281
Change-Id: I34081fcdbc40fd6635ee4e2ade01a7be39e7df25
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1609900
Reviewed-by: Boris Sazonov <bsazonov@chromium.org>
Commit-Queue: Pâris Meuleman <pmeuleman@chromium.org>
Auto-Submit: Pâris Meuleman <pmeuleman@chromium.org>
Cr-Commit-Position: refs/heads/master@{#659403}
1 file changed