Enable the -Wundef warning for clang

webrtc/modules/audio_coding/neteq/neteq_network_stats_unittest.cc

 /*
  *  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.
  */
 
 #include <memory>
 
-#include "testing/gmock/include/gmock/gmock.h"
+#include "webrtc/test/gmock.h"
 #include "webrtc/modules/audio_coding/neteq/tools/neteq_external_decoder_test.h"
 #include "webrtc/modules/audio_coding/neteq/tools/rtp_generator.h"
 #include "webrtc/modules/include/module_common_types.h"
 
 namespace webrtc {
 namespace test {
 
 using ::testing::_;
 using ::testing::SetArgPointee;
 using ::testing::Return;
@@ skipping 302 matching lines @@
 
 TEST(NetEqNetworkStatsTest, NoiseExpansionTest) {
   MockAudioDecoder decoder(48000, 1);
   NetEqNetworkStatsTest test(NetEqDecoder::kDecoderOpus, 48000, &decoder);
   test.NoiseExpansionTest();
   EXPECT_CALL(decoder, Die()).Times(1);
 }
 
 }  // namespace test
 }  // namespace webrtc