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

ui/aura/mus/window_tree_host_mus_init_params.h

Index: ui/aura/mus/window_tree_host_mus_init_params.h
diff --git a/ui/aura/mus/window_tree_host_mus_init_params.h b/ui/aura/mus/window_tree_host_mus_init_params.h
index 1cc26dd253f0b89e2d18324263376d2556707862..bf178bdc094ffb12cafa1446d42e70492009b447 100644
--- a/ui/aura/mus/window_tree_host_mus_init_params.h
+++ b/ui/aura/mus/window_tree_host_mus_init_params.h
@@ -65,6 +65,9 @@ struct AURA_EXPORT WindowTreeHostMusInitParams {
   // Used when the WindowTreeHostMus corresponds to a new display manually
   // created by the window manager.
   std::unique_ptr<DisplayInitParams> display_init_params;
+
+  // Use classic IME instead of servicified IME.
+  bool use_classic_ime = false;
 };
 
 // Creates a WindowTreeHostMusInitParams that is used when creating a top-level