Make UserActivityDetector a singleton

athena/env/athena_env_impl.cc

Index: athena/env/athena_env_impl.cc
diff --git a/athena/env/athena_env_impl.cc b/athena/env/athena_env_impl.cc
index 326b950cc567c1ca9abecd5095db12aa67c42ef9..bdb6408fea58523d4bb4a6ca13a0157356920168 100644
--- a/athena/env/athena_env_impl.cc
+++ b/athena/env/athena_env_impl.cc
@@ -197,11 +197,10 @@ class AthenaEnvImpl : public AthenaEnv,
     cursor_manager_->SetCursor(ui::kCursorPointer);
     aura::client::SetCursorClient(host_->window(), cursor_manager_.get());
 
-    user_activity_detector_.reset(new wm::UserActivityDetector);
     host_->event_processor()->GetRootTarget()->AddPreTargetHandler(
-        user_activity_detector_.get());
+        wm::UserActivityDetector::Get());
     user_activity_notifier_.reset(new ui::UserActivityPowerManagerNotifier(
-        user_activity_detector_.get()));
+        wm::UserActivityDetector::Get()));
 
     host_->AddObserver(this);
     host_->Show();
@@ -216,16 +215,13 @@ class AthenaEnvImpl : public AthenaEnv,
     host_->RemoveObserver(this);
     if (input_method_filter_)
       root_window_event_filter_->RemoveHandler(input_method_filter_.get());
-    if (user_activity_detector_) {
-      host_->event_processor()->GetRootTarget()->RemovePreTargetHandler(
-          user_activity_detector_.get());
-    }
+    host_->event_processor()->GetRootTarget()->RemovePreTargetHandler(
+        wm::UserActivityDetector::Get());
     root_window_event_filter_.reset();
     capture_client_.reset();
     input_method_filter_.reset();
     cursor_manager_.reset();
     user_activity_notifier_.reset();
-    user_activity_detector_.reset();
 
     input_method_filter_.reset();
     host_.reset();
@@ -313,7 +309,6 @@ class AthenaEnvImpl : public AthenaEnv,
   scoped_ptr<wm::CompoundEventFilter> root_window_event_filter_;
   scoped_ptr<aura::client::DefaultCaptureClient> capture_client_;
   scoped_ptr<wm::CursorManager> cursor_manager_;
-  scoped_ptr<wm::UserActivityDetector> user_activity_detector_;
   scoped_ptr<ui::DisplayConfigurator> display_configurator_;
   scoped_ptr<ui::UserActivityPowerManagerNotifier> user_activity_notifier_;