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

milo/appengine/job_source/swarming/buildLog.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 (
         "fmt"
         "path"
         "sort"
@@ skipping 49 matching lines @@
 
         if stream.Closed {
                 cached.SetValue([]byte(stream.Text))
                 if err := mc.Set(c, cached); err != nil {
                         logging.Errorf(c, "Failed to write log with key %s to memcache: %s", cached.Key(), err)
                 }
         }
 
         return stream.Text, stream.Closed, nil
 }