Use ScopedTaskEnvironment instead of MessageLoopForUI in remoting tests.

remoting/test/it2me_standalone_host.h

Index: remoting/test/it2me_standalone_host.h
diff --git a/remoting/test/it2me_standalone_host.h b/remoting/test/it2me_standalone_host.h
index c7055374dbadebdc3722323081e58b46f1deb664..5d1f6433044063a99ff184fad94440da3aa23113 100644
--- a/remoting/test/it2me_standalone_host.h
+++ b/remoting/test/it2me_standalone_host.h
@@ -9,8 +9,8 @@
 #include <string>
 
 #include "base/memory/ref_counted.h"
-#include "base/message_loop/message_loop.h"
 #include "base/run_loop.h"
+#include "base/test/scoped_task_environment.h"
 #include "base/timer/timer.h"
 #include "remoting/host/host_mock_objects.h"
 #include "remoting/host/it2me_desktop_environment.h"
@@ -43,7 +43,7 @@ class It2MeStandaloneHost {
  private:
   void Connect();
 
-  base::MessageLoopForUI message_loop_;
+  base::test::ScopedTaskEnvironment scoped_task_environment_;
   base::RunLoop run_loop_;
   std::unique_ptr<ChromotingHostContext> context_;
   scoped_refptr<AutoThreadTaskRunner> main_task_runner_;