Reland of Reimplement AccountManagerHelper singleton instance creation

components/signin/core/browser/child_account_info_fetcher_android.cc

Index: components/signin/core/browser/child_account_info_fetcher_android.cc
diff --git a/components/signin/core/browser/child_account_info_fetcher_android.cc b/components/signin/core/browser/child_account_info_fetcher_android.cc
index 654a8154e3eebad86cd49c6f3d5b92a187e0af4e..34446dad77e68b0f0cbf3950ab7182df962fe986 100644
--- a/components/signin/core/browser/child_account_info_fetcher_android.cc
+++ b/components/signin/core/browser/child_account_info_fetcher_android.cc
@@ -29,6 +29,11 @@ std::unique_ptr<ChildAccountInfoFetcher> ChildAccountInfoFetcherAndroid::Create(
       new ChildAccountInfoFetcherAndroid(service, account_id, account_name));
 }
 
+void ChildAccountInfoFetcherAndroid::InitializeForTests() {
+  Java_ChildAccountInfoFetcher_initializeForTests(
+      base::android::AttachCurrentThread());
+}
+
 ChildAccountInfoFetcherAndroid::ChildAccountInfoFetcherAndroid(
     AccountFetcherService* service,
     const std::string& account_id,