Add generators for protobuf files.
This CL contains the basic logic required to generate the protobuf
files from dawn.json and the newly added dawn_lpm.json for
libprotobuf-mutator.
Bug: chromium:1374747
Change-Id: I5dd207ed94ecdac365306c26e79b6cc18d3978f6
Reviewed-on: https://dawn-review.googlesource.com/c/dawn/+/114640
Reviewed-by: Austin Eng <enga@chromium.org>
Kokoro: Kokoro <noreply+kokoro@google.com>
Commit-Queue: Brendon Tiszka <tiszka@chromium.org>
Brendon Tiszka