Enable the -Wundef warning for clang

webrtc/modules/audio_coding/neteq/delay_peak_detector_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 DelayPeakDetector class.
 
 #include "webrtc/modules/audio_coding/neteq/delay_peak_detector.h"
 
-#include "testing/gtest/include/gtest/gtest.h"
+#include "webrtc/test/gtest.h"
 
 namespace webrtc {
 
 TEST(DelayPeakDetector, CreateAndDestroy) {
   TickTimer tick_timer;
   DelayPeakDetector* detector = new DelayPeakDetector(&tick_timer);
   EXPECT_FALSE(detector->peak_found());
   delete detector;
 }
 
@@ skipping 108 matching lines @@
   detector.SetPacketAudioLength(kPacketSizeMs);
 
   const int kTargetBufferLevel = 2;  // Define peaks to be iat > 4.
   const int kInterArrivalTime = 3 * kTargetBufferLevel;  // Will trigger a peak.
   EXPECT_FALSE(detector.Update(kInterArrivalTime, kTargetBufferLevel));
   EXPECT_FALSE(detector.Update(kInterArrivalTime, kTargetBufferLevel));
   EXPECT_FALSE(detector.Update(kInterArrivalTime, kTargetBufferLevel));
 }
 
 }  // namespace webrtc