ash: Instantiate UserActivityForwarder for --mus.

ash/shell.cc

Index: ash/shell.cc
diff --git a/ash/shell.cc b/ash/shell.cc
index 8cdfec9c861977a5c88ca323d51d7546de3f1125..60c92bd2edc7442f8a7e3f14ae3e41a45fa56872 100644
--- a/ash/shell.cc
+++ b/ash/shell.cc
@@ -984,7 +984,8 @@ void Shell::Init(const ShellInitParams& init_params) {
       display_configurator_->cached_displays());
 
   // The connector is unavailable in some tests.
-  if (config == Config::MASH && shell_delegate_->GetShellConnector()) {
+  if ((config == Config::MASH || config == Config::MUS) &&

[Daniel Erat, 2017/05/04 23:06:53]

would you recommend != Config::CLASSIC here? i'm just thinking of the case where
we decide to add yet another /m[aeiou]sh?/ config that uses ws.

[sadrul, 2017/05/04 23:09:48]

Maybe we should use aura::Env::Mode::MUS for this sort of thing (i.e. as long as
we are using mus, we would want this, regardless of which mus-config we are
using)?

[Daniel Erat, 2017/05/04 23:58:00]

sure, that seems even better. thanks!

+      shell_delegate_->GetShellConnector()) {
     ui::mojom::UserActivityMonitorPtr user_activity_monitor;
     shell_delegate_->GetShellConnector()->BindInterface(ui::mojom::kServiceName,
                                                         &user_activity_monitor);