Enable the -Wundef warning for clang

webrtc/modules/audio_coding/neteq/decision_logic_unittest.cc

 /*
  *  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.
  */
 
 // Unit tests for DecisionLogic class and derived classes.
 
-#include "testing/gtest/include/gtest/gtest.h"
+#include "webrtc/test/gtest.h"
 #include "webrtc/modules/audio_coding/codecs/mock/mock_audio_decoder_factory.h"
 #include "webrtc/modules/audio_coding/neteq/buffer_level_filter.h"
 #include "webrtc/modules/audio_coding/neteq/decoder_database.h"
 #include "webrtc/modules/audio_coding/neteq/decision_logic.h"
 #include "webrtc/modules/audio_coding/neteq/delay_manager.h"
 #include "webrtc/modules/audio_coding/neteq/delay_peak_detector.h"
 #include "webrtc/modules/audio_coding/neteq/packet_buffer.h"
 #include "webrtc/modules/audio_coding/neteq/tick_timer.h"
 
 namespace webrtc {
@@ skipping 22 matching lines @@
   delete logic;
   logic = DecisionLogic::Create(
       fs_hz, output_size_samples, kPlayoutOff, &decoder_database, packet_buffer,
       &delay_manager, &buffer_level_filter, &tick_timer);
   delete logic;
 }
 
 // TODO(hlundin): Write more tests.
 
 }  // namespace webrtc