Make the first app to request input win

services/ui/input_manager/input_associate.cc

Index: services/ui/input_manager/input_associate.cc
diff --git a/services/ui/input_manager/input_associate.cc b/services/ui/input_manager/input_associate.cc
index 7d739bce2ca900201976440d36993777413bee8a..c97f7056647dee59a122ded1222b0095cabdbed0 100644
--- a/services/ui/input_manager/input_associate.cc
+++ b/services/ui/input_manager/input_associate.cc
@@ -54,7 +54,8 @@ void InputAssociate::SetListener(mojo::ui::ViewToken* view_token,
                                  mojo::ui::InputListenerPtr listener) {
   // TODO(jeffbrown): This simple hack just hooks up the first listener
   // ever seen.
-  listener_ = listener.Pass();
+  if (!listener_)
+    listener_ = listener.Pass();
 }
 
 void InputAssociate::DispatchEvent(mojo::ui::ViewTreeToken* view_tree_token,