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

mash/browser/browser.h

Index: mash/browser/browser.h
diff --git a/mash/browser/browser.h b/mash/browser/browser.h
index ffa0cf3aee76d8eb5c85f5d51fb36a0022c1e580..29b63ae23e7a81edcd534d42f210a9293d3c1115 100644
--- a/mash/browser/browser.h
+++ b/mash/browser/browser.h
@@ -16,6 +16,7 @@
 namespace views {
 class AuraInit;
 class Widget;
+class WindowManagerConnection;
 }
 
 namespace mash {
@@ -54,6 +55,7 @@ class Browser : public shell::ShellClient,
 
   mojo::TracingImpl tracing_;
   std::unique_ptr<views::AuraInit> aura_init_;
+  std::unique_ptr<views::WindowManagerConnection> window_manager_connection_;
 
   DISALLOW_COPY_AND_ASSIGN(Browser);
 };