The new serialization scheme tries to serialize DropTargetListeners and
DragSourceListeners owned by DropTargets and DragSources, respectively. These
listeners will only be serialized if they implement Serializable. Unfortunately,
existing applications may include such listeners, but may not have written those
listeners to be serializable in practice. That is, they may contain
non-transient fields of non-Serializable types. In that case, the new
serialization scheme appears to break these existing applications. Although the
bug is fundamentally in the application, this is too big of a backward-
compatibility concern to just dump on developers.

See attachments for test case.