Make ui::test::EventGenerator work with PointerEvents in mash

ui/aura/test/mus/window_tree_client_private.h

Index: ui/aura/test/mus/window_tree_client_private.h
diff --git a/ui/aura/test/mus/window_tree_client_private.h b/ui/aura/test/mus/window_tree_client_private.h
index 78b360d7be73f91244be1395f87f62c6df38e85d..e600127b488449b17c44437e2c421ba0d59c0f31 100644
--- a/ui/aura/test/mus/window_tree_client_private.h
+++ b/ui/aura/test/mus/window_tree_client_private.h
@@ -49,6 +49,10 @@ class WindowTreeClientPrivate {
   // Pretends that |event| has been received from the window server.
   void CallOnWindowInputEvent(Window* window, std::unique_ptr<ui::Event> event);
 
+  // Simulates |event| matching a pointer watcher on the window server.
+  void CallOnPointerEventObserved(Window* window,
+                                  std::unique_ptr<ui::Event> event);
+
   void CallOnCaptureChanged(Window* new_capture, Window* old_capture);
 
   // Sets the WindowTree and client id.