Enable the -Wundef warning for clang

webrtc/modules/audio_processing/utility/delay_estimator_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.
  */
 
-#include "testing/gtest/include/gtest/gtest.h"
+#include "webrtc/test/gtest.h"
 
 #include "webrtc/modules/audio_processing/utility/delay_estimator.h"
 #include "webrtc/modules/audio_processing/utility/delay_estimator_internal.h"
 #include "webrtc/modules/audio_processing/utility/delay_estimator_wrapper.h"
 #include "webrtc/typedefs.h"
 
 namespace {
 
 enum { kSpectrumSize = 65 };
 // Delay history sizes.
@@ skipping 588 matching lines @@
   EXPECT_EQ(kDifferentHistorySize, WebRtc_history_size(handle_));
   EXPECT_EQ(0, WebRtc_InitDelayEstimator(handle_));
   EXPECT_EQ(kDifferentHistorySize, WebRtc_history_size(handle_));
   EXPECT_EQ(0, WebRtc_InitDelayEstimatorFarend(farend_handle_));
   EXPECT_EQ(kDifferentHistorySize, WebRtc_history_size(handle_));
 }
 
 // TODO(bjornv): Add tests for SoftReset...(...).
 
 }  // namespace