mustash: Connect ash system tray "show settings" items to chrome over mojo

ash/common/system/chromeos/supervised/tray_supervised_user.cc

Index: ash/common/system/chromeos/supervised/tray_supervised_user.cc
diff --git a/ash/common/system/chromeos/supervised/tray_supervised_user.cc b/ash/common/system/chromeos/supervised/tray_supervised_user.cc
index a048ef59f6ae01be6773b3f62ce951174de918c3..4f15d48a36bff344e911266da3dd786e3472d731 100644
--- a/ash/common/system/chromeos/supervised/tray_supervised_user.cc
+++ b/ash/common/system/chromeos/supervised/tray_supervised_user.cc
@@ -69,7 +69,7 @@ void TraySupervisedUser::DestroyDefaultView() {
 }
 
 void TraySupervisedUser::OnViewClicked(views::View* sender) {
-  WmShell::Get()->system_tray_delegate()->ShowSupervisedUserInfo();
+  // TODO(antrim): Find out what should we show in this case.
 }
 
 void TraySupervisedUser::UpdateAfterLoginStatusChange(LoginStatus status) {