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

milo/appengine/backends/buildbot/pubsub.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 (
         "bytes"
         "compress/gzip"
         "compress/zlib"
@@ skipping 387 matching lines @@
 
         }
         if master != nil {
                 code := doMaster(c, master, internal)
                 if code != 0 {
                         return code
                 }
         }
         return http.StatusOK
 }