Enable the -Wundef warning for clang

webrtc/modules/audio_coding/acm2/initial_delay_manager_unittest.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 <string.h>
 
 #include <memory>
 
-#include "testing/gtest/include/gtest/gtest.h"
+#include "webrtc/base/gtest.h"
 #include "webrtc/modules/audio_coding/acm2/initial_delay_manager.h"
 
 namespace webrtc {
 
 namespace acm2 {
 
 namespace {
 
 const uint8_t kAudioPayloadType = 0;
 const uint8_t kCngPayloadType = 1;
@@ skipping 343 matching lines @@
   manager_->UpdateLastReceivedPacket(rtp_info_, rtp_receive_timestamp_,
                                      InitialDelayManager::kAudioPacket,
                                      false, kSamplingRateHz, &sync_stream);
   EXPECT_EQ(0, sync_stream.num_sync_packets);
   EXPECT_FALSE(manager_->buffering());
 }
 
 }  // namespace acm2
 
 }  // namespace webrtc