Enable the -Wundef warning for clang

webrtc/modules/audio_coding/test/PCMFile.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 "webrtc/modules/audio_coding/test/PCMFile.h"
 
 #include <ctype.h>
 #include <stdio.h>
 #include <string.h>
 
-#include "testing/gtest/include/gtest/gtest.h"
+#include "webrtc/test/gtest.h"
 #include "webrtc/modules/include/module_common_types.h"
 
 namespace webrtc {
 
 #define MAX_FILE_NAME_LENGTH_BYTE 500
 
 PCMFile::PCMFile()
     : pcm_file_(NULL),
       samples_10ms_(160),
       frequency_(16000),
@@ skipping 190 matching lines @@
 
 void PCMFile::ReadStereo(bool is_stereo) {
   read_stereo_ = is_stereo;
 }
 
 void PCMFile::SetNum10MsBlocksToRead(int value) {
   num_10ms_blocks_to_read_ = rtc::Optional<int>(value);
 }
 
 }  // namespace webrtc