Change gae to apache 2 license.

service/mail/message.go

-// Copyright 2015 The Chromium Authors. All rights reserved.
-// Use of this source code is governed by a BSD-style license that can be
-// found in the LICENSE file.
+// 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 mail
 
 import (
         "fmt"
         net_mail "net/mail"
         "reflect"
 
         "google.golang.org/appengine/mail"
 )
@@ skipping 109 matching lines @@
                 }
         }
 
         if len(m.Attachments) > 0 {
                 ret.Attachments = make([]Attachment, len(m.Attachments))
                 copy(ret.Attachments, m.Attachments)
         }
 
         return &ret
 }