Enable the -Wundef warning for clang

webrtc/modules/audio_coding/neteq/mock/mock_decoder_database.h

 /*
  *  Copyright (c) 2012 The WebRTC project authors. All Rights Reserved.
  *
  *  Use of this source code is governed by a BSD-style license
  *  that can be found in the LICENSE file in the root of the source
  *  tree. An additional intellectual property rights grant can be found
  *  in the file PATENTS.  All contributing project authors may
  *  be found in the AUTHORS file in the root of the source tree.
  */
 
 #ifndef WEBRTC_MODULES_AUDIO_CODING_NETEQ_MOCK_MOCK_DECODER_DATABASE_H_
 #define WEBRTC_MODULES_AUDIO_CODING_NETEQ_MOCK_MOCK_DECODER_DATABASE_H_
 
 #include <string>
 
 #include "webrtc/modules/audio_coding/neteq/decoder_database.h"
 
-#include "testing/gmock/include/gmock/gmock.h"
+#include "webrtc/test/gmock.h"
 
 namespace webrtc {
 
 class MockDecoderDatabase : public DecoderDatabase {
  public:
   explicit MockDecoderDatabase(
       rtc::scoped_refptr<AudioDecoderFactory> factory = nullptr)
       : DecoderDatabase(factory) {}
   virtual ~MockDecoderDatabase() { Die(); }
   MOCK_METHOD0(Die, void());
@@ skipping 21 matching lines @@
   MOCK_CONST_METHOD0(GetActiveDecoder,
       AudioDecoder*());
   MOCK_METHOD1(SetActiveCngDecoder,
       int(uint8_t rtp_payload_type));
   MOCK_CONST_METHOD0(GetActiveCngDecoder,
       ComfortNoiseDecoder*());
 };
 
 }  // namespace webrtc
 #endif  // WEBRTC_MODULES_AUDIO_CODING_NETEQ_MOCK_MOCK_DECODER_DATABASE_H_