Use ScopedTaskEnvironment instead of MessageLoopForUI in components tests.

components/sync/driver/async_directory_type_controller_unittest.cc

Index: components/sync/driver/async_directory_type_controller_unittest.cc
diff --git a/components/sync/driver/async_directory_type_controller_unittest.cc b/components/sync/driver/async_directory_type_controller_unittest.cc
index c28c2bbad80ce3150135a15e5505d9bebcbcbb2f..fe611899592aa8c0fdd668b1337466b2568b7e00 100644
--- a/components/sync/driver/async_directory_type_controller_unittest.cc
+++ b/components/sync/driver/async_directory_type_controller_unittest.cc
@@ -16,6 +16,7 @@
 #include "base/run_loop.h"
 #include "base/single_thread_task_runner.h"
 #include "base/synchronization/waitable_event.h"
+#include "base/test/scoped_task_environment.h"
 #include "base/test/test_timeouts.h"
 #include "base/threading/thread.h"
 #include "base/threading/thread_task_runner_handle.h"
@@ -177,7 +178,10 @@ class AsyncDirectoryTypeControllerFake : public AsyncDirectoryTypeController {
 class SyncAsyncDirectoryTypeControllerTest : public testing::Test,
                                              public FakeSyncClient {
  public:
-  SyncAsyncDirectoryTypeControllerTest() : backend_thread_("dbthread") {}
+  SyncAsyncDirectoryTypeControllerTest()
+      : scoped_task_environment_(
+            base::test::ScopedTaskEnvironment::MainThreadType::UI),
+        backend_thread_("dbthread") {}
 
   void SetUp() override {
     backend_thread_.Start();
@@ -253,7 +257,7 @@ class SyncAsyncDirectoryTypeControllerTest : public testing::Test,
 
   static void SignalDone(WaitableEvent* done) { done->Signal(); }
 
-  base::MessageLoopForUI message_loop_;
+  base::test::ScopedTaskEnvironment scoped_task_environment_;
   base::Thread backend_thread_;
 
   StartCallbackMock start_callback_;