Right, the grpc-java part got merged a little before the full system was ready since we could already test it out. Feel free to try out the compiler from the PR, though! The content is there and ready for folks to experiment with. In fact, I've approved the code, but haven't merged it yet because I want to make sure that the installation is truly seamless.
We'd appreciate any feedback that you have on it: it's still an early experimental version, but we'll move it forward as we get more users for it.