Have OAuthMultilogin classes explicitly take in ProfileOAuth2TokenService

As part of the effort to eliminate OAuth2TokenService, this CL ports
the OAuthMultilogin classes to explicitly use ProfileOAuth2TokenService
(which is what they are always passed in production). This entails
changes in the unittest to use FakeProfileOAuth2TokenService rather than
FakeOAuth2TokenService. That change is good :), as we will be
eliminating FakeOAuth2TokenService as well.

Note that it is not possible to change these classes to instead take in
OAuth2AccessTokenManager, as the OAuth2TokenService APIs that they use
will stay on ProfileOAuth2TokenService long-term.

Bug: 967598
Change-Id: Ie4b3c770da2ea2d6b51828d78132895a3ba49f13
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1679752
Commit-Queue: Colin Blundell <blundell@chromium.org>
Reviewed-by: Sylvain Defresne <sdefresne@chromium.org>
Cr-Commit-Position: refs/heads/master@{#673261}