Desugar-singlejar integration tests for double-checking default methods.

PiperOrigin-RevId: 171980809
GitOrigin-RevId: 9cf05abe06ee687d21e8a5bb12399a33f3fe0498
Change-Id: I4995c684a6d1d7440a125e1f56daa47209c60cdc
5 files changed
tree: a132ae4c3be099d7fd678b0ad7587ce6c54218c8
  1. java/
  2. test/