mus: Implement ScreenMus::GetCursorScreenPoint().

components/mus/ws/event_dispatcher.cc

Index: components/mus/ws/event_dispatcher.cc
diff --git a/components/mus/ws/event_dispatcher.cc b/components/mus/ws/event_dispatcher.cc
index 7dce130a2d57038272214239f960ddf0458a1547..b2eaf996820b768610e02672878070dff66ae1b0 100644
--- a/components/mus/ws/event_dispatcher.cc
+++ b/components/mus/ws/event_dispatcher.cc
@@ -108,6 +108,7 @@ void EventDispatcher::SetMousePointerScreenLocation(
   DCHECK(pointer_targets_.empty());
   mouse_pointer_last_location_ = screen_location;
   UpdateCursorProviderByLastKnownLocation();
+  delegate_->OnMouseCursorLocationChanged(screen_location);
 }
 
 bool EventDispatcher::SetCaptureWindow(ServerWindow* window,
@@ -239,8 +240,10 @@ void EventDispatcher::ProcessLocatedEvent(const ui::LocatedEvent& event) {
   const bool is_mouse_event =
       event.IsMousePointerEvent() || event.IsMouseWheelEvent();
 
-  if (is_mouse_event)
+  if (is_mouse_event) {
+    delegate_->OnMouseCursorLocationChanged(event.root_location());

[sky, 2016/04/20 23:46:36]

nit: move this after 245 so the mouse_pointer_last_location_ has been set
appropriately (like you do on 111).

     mouse_pointer_last_location_ = event.location();
+  }
 
   // Release capture on pointer up. For mouse we only release if there are
   // no buttons down.