Enable the -Wundef warning for clang

webrtc/test/mock_voe_channel_proxy.h

 /*
  *  Copyright (c) 2015 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_TEST_MOCK_VOE_CHANNEL_PROXY_H_
 #define WEBRTC_TEST_MOCK_VOE_CHANNEL_PROXY_H_
 
 #include <string>
-#include "testing/gmock/include/gmock/gmock.h"
+#include "webrtc/test/gmock.h"
 #include "webrtc/voice_engine/channel_proxy.h"
 
 namespace webrtc {
 namespace test {
 
 class MockVoEChannelProxy : public voe::ChannelProxy {
  public:
   MOCK_METHOD1(SetRTCPStatus, void(bool enable));
   MOCK_METHOD1(SetLocalSSRC, void(uint32_t ssrc));
   MOCK_METHOD1(SetRTCP_CNAME, void(const std::string& c_name));
@@ skipping 31 matching lines @@
   MOCK_CONST_METHOD0(GetAudioDecoderFactory,
                      const rtc::scoped_refptr<AudioDecoderFactory>&());
   MOCK_METHOD1(SetChannelOutputVolumeScaling, void(float scaling));
   MOCK_METHOD1(SetRtcEventLog, void(RtcEventLog* event_log));
   MOCK_METHOD1(SetBitrate, void(int bitrate_bps));
 };
 }  // namespace test
 }  // namespace webrtc
 
 #endif  // WEBRTC_TEST_MOCK_VOE_CHANNEL_PROXY_H_