Enable the -Wundef warning for clang

webrtc/modules/audio_coding/neteq/tools/neteq_external_decoder_test.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 "webrtc/modules/audio_coding/neteq/tools/neteq_external_decoder_test.h"
 
 #include "webrtc/modules/audio_coding/codecs/builtin_audio_decoder_factory.h"
-#include "testing/gtest/include/gtest/gtest.h"
+#include "webrtc/test/gtest.h"
 #include "webrtc/base/format_macros.h"
 
 namespace webrtc {
 namespace test {
 
 NetEqExternalDecoderTest::NetEqExternalDecoderTest(NetEqDecoder codec,
                                                    int sample_rate_hz,
                                                    AudioDecoder* decoder)
     : codec_(codec),
       decoder_(decoder),
@@ skipping 24 matching lines @@
   EXPECT_EQ(NetEq::kOK, neteq_->GetAudio(output, &muted));
   ASSERT_FALSE(muted);
   EXPECT_EQ(channels_, output->num_channels_);
   EXPECT_EQ(static_cast<size_t>(kOutputLengthMs * sample_rate_hz_ / 1000),
             output->samples_per_channel_);
   EXPECT_EQ(sample_rate_hz_, neteq_->last_output_sample_rate_hz());
 }
 
 }  // namespace test
 }  // namespace webrtc