Enable the -Wundef warning for clang

webrtc/modules/audio_processing/beamformer/mock_nonlinear_beamformer.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_MODULES_AUDIO_PROCESSING_BEAMFORMER_MOCK_BEAMFORMER_H_
 #define WEBRTC_MODULES_AUDIO_PROCESSING_BEAMFORMER_MOCK_BEAMFORMER_H_
 
 #include <vector>
 
-#include "testing/gmock/include/gmock/gmock.h"
+#include "webrtc/test/gmock.h"
 #include "webrtc/modules/audio_processing/beamformer/nonlinear_beamformer.h"
 
 namespace webrtc {
 
 class MockNonlinearBeamformer : public NonlinearBeamformer {
  public:
   MockNonlinearBeamformer(const std::vector<Point>& array_geometry,
                           size_t num_postfilter_channels)
       : NonlinearBeamformer(array_geometry, num_postfilter_channels) {}
 
   MockNonlinearBeamformer(const std::vector<Point>& array_geometry)
       : NonlinearBeamformer(array_geometry, 1u) {}
 
   MOCK_METHOD2(Initialize, void(int chunk_size_ms, int sample_rate_hz));
   MOCK_METHOD1(AnalyzeChunk, void(const ChannelBuffer<float>& data));
   MOCK_METHOD1(PostFilter, void(ChannelBuffer<float>* data));
   MOCK_METHOD1(IsInBeam, bool(const SphericalPointf& spherical_point));
   MOCK_METHOD0(is_target_present, bool());
 };
 
 }  // namespace webrtc
 
 #endif  // WEBRTC_MODULES_AUDIO_PROCESSING_BEAMFORMER_MOCK_BEAMFORMER_H_