Dart LUCI buildbucket protobufs.
These protobufs are used to communicate with LUCI Buildbucket services from Dart Language.
Regenerating the protos
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.
File an issue in flutter/flutter with the word 'buildbucket-dart' clearly in the title and cc @godofredoc.