Change gae to apache 2 license.

impl/memory/mail.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 memory
 
 import (
         "fmt"
         net_mail "net/mail"
         "net/textproto"
         "path/filepath"
         "strings"
         "sync"
@@ skipping 180 matching lines @@
                 ret[i] = m.Copy()
         }
         return ret
 }
 
 func (m *mailImpl) Reset() {
         m.data.Lock()
         m.data.queue = nil
         m.data.Unlock()
 }