Enable the -Wundef warning for clang

webrtc/modules/video_coding/test/stream_generator.cc

 /*
  *  Copyright (c) 2013 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/video_coding/test/stream_generator.h"
 
 #include <string.h>
 
 #include <list>
 
-#include "testing/gtest/include/gtest/gtest.h"
+#include "webrtc/test/gtest.h"
 #include "webrtc/modules/video_coding/packet.h"
 #include "webrtc/modules/video_coding/test/test_util.h"
 #include "webrtc/system_wrappers/include/clock.h"
 
 namespace webrtc {
 
 StreamGenerator::StreamGenerator(uint16_t start_seq_num, int64_t current_time)
     : packets_(), sequence_number_(start_seq_num), start_time_(current_time) {}
 
 void StreamGenerator::Init(uint16_t start_seq_num, int64_t current_time) {
@@ skipping 93 matching lines @@
   std::list<VCMPacket>::iterator it = packets_.begin();
   for (int i = 0; i < index; ++i) {
     ++it;
     if (it == packets_.end())
       break;
   }
   return it;
 }
 
 }  // namespace webrtc