Move ActiveAccountAccessTokenFetcherImpl into DeviceIdentityProvider

This class provides an implementation of
ActiveAccountAccessTokenFetcher that is backed by
DeviceOAuth2TokenService. With the pending removal of
OAuth2TokenService, the class needs to live in //chrome where it can
have direct knowledge of DeviceOAuth2TokenService. This CL makes that
change.

Bug: 967598
Change-Id: I585dc5b0f27dad7051256f0550867e23733d85d0
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1675550
Reviewed-by: Mihai Sardarescu <msarda@chromium.org>
Commit-Queue: Colin Blundell <blundell@chromium.org>
Cr-Commit-Position: refs/heads/master@{#672058}
5 files changed