Revert of Reimplement AccountManagerHelper singleton instance creation

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 284cefb23bb275f1e4f28baf718ecfef9b098a0a..9fae742506b36d9356adcbaa70a731f2911cabe2 100644
--- a/components/signin/core/browser/account_tracker_service_unittest.cc
+++ b/components/signin/core/browser/account_tracker_service_unittest.cc
@@ -15,7 +15,6 @@
 #include "components/signin/core/browser/account_fetcher_service.h"
 #include "components/signin/core/browser/account_info.h"
 #include "components/signin/core/browser/account_tracker_service.h"
-#include "components/signin/core/browser/child_account_info_fetcher.h"
 #include "components/signin/core/browser/fake_account_fetcher_service.h"
 #include "components/signin/core/browser/test_signin_client.h"
 #include "components/signin/core/common/signin_pref_names.h"
@@ -256,8 +255,6 @@
   ~AccountTrackerServiceTest() override {}
 
   void SetUp() override {
-    ChildAccountInfoFetcher::InitializeForTests();
-
     fake_oauth2_token_service_.reset(new FakeOAuth2TokenService());
 
     pref_service_.registry()->RegisterListPref(