Fix an interactive ui test

ui/aura/window_event_dispatcher.cc

Index: ui/aura/window_event_dispatcher.cc
diff --git a/ui/aura/window_event_dispatcher.cc b/ui/aura/window_event_dispatcher.cc
index 559c9524748a85e10b0cb0fc40780d28baeb5aef..0361ce6e737e0e10fd4bbd39b7ce054e7e3ca398 100644
--- a/ui/aura/window_event_dispatcher.cc
+++ b/ui/aura/window_event_dispatcher.cc
@@ -314,6 +314,10 @@ ui::EventDispatchDetails WindowEventDispatcher::ProcessGestures(
     details = DispatchEvent(target, event.get());
     if (details.dispatcher_destroyed || details.target_destroyed)
       break;
+    // If the target window has moved off to a different WindowTreeHost, then
+    // abort processing the rest of the events.
+    if (!window()->Contains(target))
+      break;
   }
   return details;
 }