[milo] build_source -> buildSource.

milo/buildsource/swarming/build_test.go

 // Copyright 2015 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 swarming
 
 import (
         "encoding/json"
         "flag"
         "fmt"
@@ skipping 102 matching lines @@
                                         })
                                 }
 
                                 build, err := bl.swarmingBuildImpl(c, svc, "foo", tc.name)
                                 So(err, ShouldBeNil)
                                 So(build, shouldMatchExpectationsFor, tc.name+".json")
                         })
                 }
         })
 }