Refactor AO2TS to make it easier to componentize.

components/signin/core/browser/account_tracker_service_unittest.cc

Index: components/signin/core/browser/account_tracker_service_unittest.cc
diff --git a/components/signin/core/browser/account_tracker_service_unittest.cc b/components/signin/core/browser/account_tracker_service_unittest.cc
index 3ea1ab4119ed87dffbe38cefbd34f07c1370ea6c..13c6549ef646841acc308d07c6eecbfd82f1033c 100644
--- a/components/signin/core/browser/account_tracker_service_unittest.cc
+++ b/components/signin/core/browser/account_tracker_service_unittest.cc
@@ -264,11 +264,12 @@ class AccountTrackerServiceTest : public testing::Test {
   }
 
   void SimulateTokenAvailable(const std::string& account_id) {
-    fake_oauth2_token_service_->AddAccount(account_id);
+    fake_oauth2_token_service_->GetDelegate()->UpdateCredentials(
+        account_id, "refresh_token");
   }
 
   void SimulateTokenRevoked(const std::string& account_id) {
-    fake_oauth2_token_service_->RemoveAccount(account_id);
+    fake_oauth2_token_service_->GetDelegate()->RevokeCredentials(account_id);
   }
 
   // Helpers to fake access token and user info fetching