[views-mus] Prevent creating a native OzonePlatform in mus tests.

ui/views/mus/views_mus_test_suite.cc

Index: ui/views/mus/views_mus_test_suite.cc
diff --git a/ui/views/mus/views_mus_test_suite.cc b/ui/views/mus/views_mus_test_suite.cc
index 86b748839e150b88e1a10d9660706f8e3478087a..8483a258cbe2c4fc8b1b647c1f306a7eae480931 100644
--- a/ui/views/mus/views_mus_test_suite.cc
+++ b/ui/views/mus/views_mus_test_suite.cc
@@ -261,4 +261,12 @@ void ViewsMusTestSuite::Shutdown() {
   ViewsTestSuite::Shutdown();
 }
 
+void ViewsMusTestSuite::InitializeEnv() {
+  env_ = aura::Env::CreateInstance(aura::Env::Mode::MUS);
+}
+
+void ViewsMusTestSuite::DestroyEnv() {
+  env_.reset();
+}
+
 }  // namespace views