code: func makeBuild(params httprouter.Params, build *ui.MiloBuildLegacy) *buildbucketpb.Build {
  	return &buildbucketpb.Build{
  		Builder: &buildbucketpb.BuilderID{
  			Project: build.Trigger.Project,           // equivalent params.ByName("project")
  			Bucket:  params.ByName("bucket"),         // way to get from ui.MiloBuildLegacy so don't need params here?
  			Builder: build.Summary.ParentLabel.Label, // params.ByName("builder")
  		},
  	}
  }
docs: // makeBuild partially populates a buildbucketpb.Build. Currently it attempts to
  // make available .Builder.Project, .Builder.Bucket, and .Builder.Builder.