Quit the message loop by default in ShellConnectionLost when ApplicationRunner is used

mash/wm/window_manager_application.cc

Index: mash/wm/window_manager_application.cc
diff --git a/mash/wm/window_manager_application.cc b/mash/wm/window_manager_application.cc
index 4c1bb6671a93737dac4c936ea5f2938e6621b951..c9195ccf58f2f64e8d0208badebbea50a2bebdf2 100644
--- a/mash/wm/window_manager_application.cc
+++ b/mash/wm/window_manager_application.cc
@@ -127,10 +127,6 @@ bool WindowManagerApplication::AcceptConnection(mojo::Connection* connection) {
   return true;
 }
 
-void WindowManagerApplication::ShellConnectionLost() {
-  _exit(1);
-}
-
 void WindowManagerApplication::Create(
     mojo::Connection* connection,
     mojo::InterfaceRequest<mash::wm::mojom::UserWindowController> request) {