mus: Add UserActivityMonitor.

components/mus/ws/window_manager_state.cc

Index: components/mus/ws/window_manager_state.cc
diff --git a/components/mus/ws/window_manager_state.cc b/components/mus/ws/window_manager_state.cc
index 8139b49a6d7fe4a01e87f7f18c4d1d2a129b52b4..16a5a499df264574cdc042e4b38478e669b83ef4 100644
--- a/components/mus/ws/window_manager_state.cc
+++ b/components/mus/ws/window_manager_state.cc
@@ -10,6 +10,7 @@
 #include "components/mus/ws/display_manager.h"
 #include "components/mus/ws/platform_display.h"
 #include "components/mus/ws/server_window.h"
+#include "components/mus/ws/user_activity_monitor.h"
 #include "components/mus/ws/user_display_manager.h"
 #include "components/mus/ws/user_id_tracker.h"
 #include "components/mus/ws/window_manager_display_root.h"
@@ -94,7 +95,10 @@ WindowManagerState::QueuedEvent::QueuedEvent() {}
 WindowManagerState::QueuedEvent::~QueuedEvent() {}
 
 WindowManagerState::WindowManagerState(WindowTree* window_tree)
-    : window_tree_(window_tree), event_dispatcher_(this), weak_factory_(this) {
+    : window_tree_(window_tree),
+      user_activity_monitor_(new UserActivityMonitor(nullptr)),
+      event_dispatcher_(this),
+      weak_factory_(this) {
   frame_decoration_values_ = mojom::FrameDecorationValues::New();
   frame_decoration_values_->max_title_bar_button_width = 0u;
 
@@ -179,6 +183,7 @@ void WindowManagerState::Deactivate() {
 }
 
 void WindowManagerState::ProcessEvent(const ui::Event& event) {
+  user_activity_monitor_->OnUserActivity();
   // If this is still waiting for an ack from a previously sent event, then
   // queue up the event to be dispatched once the ack is received.
   if (event_ack_timer_.IsRunning()) {