[milo] build_source -> buildSource.

milo/buildsource/buildbot/buildinfo_test.go

 // Copyright 2017 The LUCI Authors. All rights reserved.
 // Use of this source code is governed under the Apache License, Version 2.0
 // that can be found in the LICENSE file.
 
 package buildbot
 
 import (
         "testing"
 
         miloProto "github.com/luci/luci-go/common/proto/milo"
@@ skipping 356 matching lines @@
                                 },
                                 AnnotationStream: &miloProto.LogdogStream{
                                         Server: "example.com",
                                         Prefix: "bb/foo_master/bar_builder/1337",
                                         Name:   "annotations",
                                 },
                         })
                 })
         })
 }