Enable the -Wundef warning for clang

webrtc/modules/remote_bitrate_estimator/test/bwe_test_framework_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 "webrtc/modules/remote_bitrate_estimator/test/bwe_test_framework.h"
 
 #include <numeric>
 
-#include "testing/gtest/include/gtest/gtest.h"
+#include "webrtc/test/gtest.h"
 #include "webrtc/base/constructormagic.h"
 #include "webrtc/modules/remote_bitrate_estimator/test/packet.h"
 #include "webrtc/modules/remote_bitrate_estimator/test/packet_sender.h"
 #include "webrtc/test/testsupport/fileutils.h"
 
 namespace webrtc {
 namespace testing {
 namespace bwe {
 
 static bool IsSequenceNumberSorted(const Packets& packets) {
@@ skipping 940 matching lines @@
   RembFeedback* feedback = new RembFeedback(0, 0, 0, 512000, RTCPReportBlock());
   Packets packets;
   packets.push_back(feedback);
   sender.RunFor(0, &packets);
   EXPECT_EQ(820000u, source.bits_per_second());
   TestVideoSender(&sender, 10000, 1000, 500, 1025000);
 }
 }  // namespace bwe
 }  // namespace testing
 }  // namespace webrtc