'DelegateImplementation' is a variation of 'ManuallyImplement'.
'ManuallyImplement' emits the interface method, but suppresses
the Java and native-code implementation.
The latter shall be implemented manually by the user.
'DelegateImplementation' emits the interface method,
and the renamed Java and native-code implementation.
Both can be called from the manual user implementation,
Editing troubles, moved to Bug 1144.