Use ScopedTaskEnvironment instead of MessageLoop in components unit tests.

components/autofill/core/browser/autocomplete_history_manager_unittest.cc

Index: components/autofill/core/browser/autocomplete_history_manager_unittest.cc
diff --git a/components/autofill/core/browser/autocomplete_history_manager_unittest.cc b/components/autofill/core/browser/autocomplete_history_manager_unittest.cc
index df3820d9128352a925376034ea8b0566d86b9d78..56c8d274114430308f791aa80a829c9c28903881 100644
--- a/components/autofill/core/browser/autocomplete_history_manager_unittest.cc
+++ b/components/autofill/core/browser/autocomplete_history_manager_unittest.cc
@@ -10,6 +10,7 @@
 #include "base/strings/string16.h"
 #include "base/strings/utf_string_conversions.h"
 #include "base/synchronization/waitable_event.h"
+#include "base/test/scoped_task_environment.h"
 #include "base/threading/thread_task_runner_handle.h"
 #include "components/autofill/core/browser/autocomplete_history_manager.h"
 #include "components/autofill/core/browser/autofill_external_delegate.h"
@@ -78,7 +79,7 @@ class AutocompleteHistoryManagerTest : public testing::Test {
 
   void TearDown() override { autocomplete_manager_.reset(); }
 
-  base::MessageLoop message_loop_;
+  base::test::ScopedTaskEnvironment scoped_task_environment_;
   scoped_refptr<MockWebDataService> web_data_service_;
   std::unique_ptr<AutocompleteHistoryManager> autocomplete_manager_;
   std::unique_ptr<AutofillDriver> autofill_driver_;