I copied this entry from vnames.json.

Before this change, extracting the kythe repo using the bazel-extractor image results in this entry in required_inputs for protos that depend on descriptor.proto:

      "v_name": {
        "corpus": "CORPUS",
        "root": "bazel-out/bin/external/com_google_protobuf",
        "path": "src/google/protobuf/_virtual_imports/descriptor_proto/google/protobuf/descriptor.proto"
      },

After this change, we get:

      "v_name": {
        "corpus": "CORPUS",
        "root": "bazel-out/bin",
        "path": "google/protobuf/descriptor.proto"
      },

This extraction change should fix errors we've been seeing where the indexer is unable to find descriptor.proto (or other external protos) and fails.