mus: Change PointerWatcher to observe all pointer events, with moves optional.

services/ui/demo/mus_demo.cc

Index: services/ui/demo/mus_demo.cc
diff --git a/services/ui/demo/mus_demo.cc b/services/ui/demo/mus_demo.cc
index 3710de8d30fced9718230035536fb8a988fd0608..a5ce17bc0eaa32718a59d758281d37f6e5edefbc 100644
--- a/services/ui/demo/mus_demo.cc
+++ b/services/ui/demo/mus_demo.cc
@@ -84,7 +84,8 @@ void MusDemo::OnDidDestroyClient(WindowTreeClient* client) {
   timer_.Stop();
 }
 
-void MusDemo::OnEventObserved(const Event& event, Window* target) {}
+void MusDemo::OnPointerEventObserved(const PointerEvent& event,
+                                     Window* target) {}
 
 void MusDemo::SetWindowManagerClient(WindowManagerClient* client) {}