Use ScopedTaskEnvironment instead of MessageLoop in components unit tests.

components/autofill/core/browser/autofill_metrics_unittest.cc

Index: components/autofill/core/browser/autofill_metrics_unittest.cc
diff --git a/components/autofill/core/browser/autofill_metrics_unittest.cc b/components/autofill/core/browser/autofill_metrics_unittest.cc
index 306d2474e07cad399c07fd9f077d9a2a449c958a..c9fd25a046a0fc56ec6e47151179f525531f1c81 100644
--- a/components/autofill/core/browser/autofill_metrics_unittest.cc
+++ b/components/autofill/core/browser/autofill_metrics_unittest.cc
@@ -18,6 +18,7 @@
 #include "base/strings/utf_string_conversions.h"
 #include "base/test/histogram_tester.h"
 #include "base/test/scoped_feature_list.h"
+#include "base/test/scoped_task_environment.h"
 #include "base/test/user_action_tester.h"
 #include "base/time/time.h"
 #include "components/autofill/core/browser/autofill_experiments.h"
@@ -333,7 +334,7 @@ class AutofillMetricsTest : public testing::Test {
   void EnableWalletSync();
   void EnableUkmLogging();
 
-  base::MessageLoop message_loop_;
+  base::test::ScopedTaskEnvironment scoped_task_environment_;
   TestAutofillClient autofill_client_;
   std::unique_ptr<AccountTrackerService> account_tracker_;
   std::unique_ptr<FakeSigninManagerBase> signin_manager_;