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

mash/webtest/webtest.h

Index: mash/webtest/webtest.h
diff --git a/mash/webtest/webtest.h b/mash/webtest/webtest.h
index c9734176c1876bf6e34f7914e94ee498ce088022..723d67fac2cb934826e3924c89243c773af0ac55 100644
--- a/mash/webtest/webtest.h
+++ b/mash/webtest/webtest.h
@@ -16,6 +16,7 @@
 namespace views {
 class AuraInit;
 class Widget;
+class WindowManagerConnection;
 }
 
 namespace mash {
@@ -52,6 +53,7 @@ class Webtest
 
   mojo::TracingImpl tracing_;
   std::unique_ptr<views::AuraInit> aura_init_;
+  std::unique_ptr<views::WindowManagerConnection> views_mus_;
 
   DISALLOW_COPY_AND_ASSIGN(Webtest);
 };