[milo] {buildbucket,buildbot,swarming,logdog} -> backends/*.

milo/appengine/job_source/buildbot/builder.go

 // Copyright 2016 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 (
         "crypto/sha1"
         "encoding/base64"
         "errors"
@@ skipping 278 matching lines @@
         }
         result.CurrentBuilds = currentBuilds
 
         for _, fb := range finishedBuilds {
                 if fb != nil {
                         result.FinishedBuilds = append(result.FinishedBuilds, fb)
                 }
         }
         return result, nil
 }