Enable Config::MUS to use classic IME instead of servicified IME.

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 1773510cac7b77c88f0f4156684d50b4382f3026..06f3593f882061a2f3e8488ef1aa9401e3e961b8 100644
--- a/ui/views/mus/views_mus_test_suite.cc
+++ b/ui/views/mus/views_mus_test_suite.cc
@@ -111,7 +111,10 @@ class PlatformTestHelperMus : public PlatformTestHelper {
     aura::WindowTreeHostMus* window_tree_host_mus =
         static_cast<aura::WindowTreeHostMus*>(
             static_cast<DesktopNativeWidgetAura*>(native_widget)->host());
-    aura::InputMethodMusTestApi::Disable(window_tree_host_mus->input_method());
+    aura::InputMethodMus* input_method_mus =
+        window_tree_host_mus->input_method_mus_for_testing();
+    DCHECK(input_method_mus);
+    aura::InputMethodMusTestApi::Disable(input_method_mus);
     return native_widget;
   }