MESOS-7656, we have updated the JSON <=> protobuf message conversion in stout for map support which means we can use the native protobuf map feature now in Mesos code. So we should replace the manual parsing for the following fields with the native protobuf map.
Please note, for Appc image manifest, we also have a field repeated Label labels = 4, but we should not replace it with the native protobuf map support, because according to the Appc image spec, this field is not a map, instead it is a list of objects.
And in mesos.proto, we also have a couple protobuf messages which have field like optional Labels labels = 10, .e.g. TaskInfo.labels, I would not suggest to replace them with native protobuf map since that would be an API changes which may break framework's code.