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 69d7fa155ecaf903264d89c6736a20eb9dd75b5a..0e551a4e9f2c47121c84fe3c16d71cd414c91a65 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);

[sky, 2016/04/27 20:10:28]

I worry that the way you have things results in updating the client before
sending events. How about adding a comment to this effect that we're hoping this
won't cause problems.

 }
 
 bool EventDispatcher::SetCaptureWindow(ServerWindow* window,
@@ -241,8 +242,10 @@ void EventDispatcher::ProcessLocatedEvent(const ui::LocatedEvent& event) {
   const bool is_mouse_event =
       event.IsMousePointerEvent() || event.IsMouseWheelEvent();
 
-  if (is_mouse_event)
+  if (is_mouse_event) {
     mouse_pointer_last_location_ = event.location();
+    delegate_->OnMouseCursorLocationChanged(event.root_location());
+  }
 
   // Release capture on pointer up. For mouse we only release if there are
   // no buttons down.