Enable the -Wundef warning for clang

webrtc/modules/audio_coding/neteq/test/neteq_performance_unittest.cc

 /*
  *  Copyright (c) 2014 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 "testing/gtest/include/gtest/gtest.h"
+#include "webrtc/test/gtest.h"
 #include "webrtc/modules/audio_coding/neteq/tools/neteq_performance_test.h"
 #include "webrtc/test/testsupport/perf_test.h"
 #include "webrtc/typedefs.h"
 
 // Runs a test with 10% packet losses and 10% clock drift, to exercise
 // both loss concealment and time-stretching code.
 TEST(NetEqPerformanceTest, Run) {
   const int kSimulationTimeMs = 10000000;
   const int kLossPeriod = 10;  // Drop every 10th packet.
   const double kDriftFactor = 0.1;
@@ skipping 10 matching lines @@
 TEST(NetEqPerformanceTest, RunClean) {
   const int kSimulationTimeMs = 10000000;
   const int kLossPeriod = 0;  // No losses.
   const double kDriftFactor = 0.0;  // No clock drift.
   int64_t runtime = webrtc::test::NetEqPerformanceTest::Run(
       kSimulationTimeMs, kLossPeriod, kDriftFactor);
   ASSERT_GT(runtime, 0);
   webrtc::test::PrintResult(
       "neteq_performance", "", "0_pl_0_drift", runtime, "ms", true);
 }