Implement ITE::SimulateSuccessfulFetchOfAccountInfo method.

This CL implement SimulateSuccessfulFetchOfAccountInfo method in
IdentityTestEnvironment to simulate account fetching using
FakeAccountFetcherService without sending network requests.

Bug: 929608
Change-Id: Ia22b79ffa5c7f0bf697113e58a96283e6e7e8cc7
Reviewed-on: https://chromium-review.googlesource.com/c/1458896
Reviewed-by: Sylvain Defresne <sdefresne@chromium.org>
Commit-Queue: Abhijeet Kandalkar <abhijeet@igalia.com>
Cr-Commit-Position: refs/heads/master@{#630252}
3 files changed