Remove the Generator::GenerateEntryPoint() APIs as they were mostly
unimplemented and not used by anything except the Tint sample app,
which now uses the new transform.
Change-Id: I1ccb303d6c3aa15e622c193d33b753e22bf39a95
Reviewed-on: https://dawn-review.googlesource.com/c/tint/+/49160
Kokoro: Kokoro <noreply+kokoro@google.com>
Reviewed-by: Ben Clayton <bclayton@google.com>
Commit-Queue: James Price <jrprice@google.com>