views/mus: Have explicit ownership of views::WindowManagerConnection.

mash/screenlock/screenlock.h

Index: mash/screenlock/screenlock.h
diff --git a/mash/screenlock/screenlock.h b/mash/screenlock/screenlock.h
index 25838f5cdd68ba24c3bcdd48e451950148f3fa14..1fe2579d7818adc9070395141d28539b942b4d6c 100644
--- a/mash/screenlock/screenlock.h
+++ b/mash/screenlock/screenlock.h
@@ -16,6 +16,7 @@
 
 namespace views {
 class AuraInit;
+class WindowManagerConnection;
 }
 
 namespace mash {
@@ -38,6 +39,7 @@ class Screenlock : public shell::ShellClient,
 
   mojo::TracingImpl tracing_;
   std::unique_ptr<views::AuraInit> aura_init_;
+  std::unique_ptr<views::WindowManagerConnection> views_mus_;
   mojo::BindingSet<session::mojom::ScreenlockStateListener> bindings_;
 
   DISALLOW_COPY_AND_ASSIGN(Screenlock);