Dart LUCI buildbucket protobufs.
These protobufs are used to communicate with LUCI Buildbucket services from Dart Language.
dart pub global activate protoc_plugin.
That will checkout protobuf, buildbucket and googleapis repositories. It will also compile the protos and generate their correspondent Dart classes.
In order to validate the changes you have made before releasing a new version you can point your project to the local directory for packages/buildbucket-dart by doing the following in your project's pubspec.yaml:
dependencies: buildbucket-dart: path: /your/path/to/packages/buildbucket-dart
File an issue in flutter/flutter with the word ‘buildbucket-dart’ clearly in the title and cc @godofredoc.