Enable the -Wundef warning for clang

webrtc/modules/remote_bitrate_estimator/test/estimators/nada_unittest.cc

 /*
  *  Copyright (c) 2015 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/estimators/nada.h"
 
 #include <algorithm>
 #include <memory>
 #include <numeric>
 
 #include "webrtc/base/arraysize.h"
 #include "webrtc/base/common.h"
 #include "webrtc/modules/remote_bitrate_estimator/test/bwe_test_framework.h"
 #include "webrtc/modules/remote_bitrate_estimator/test/packet.h"
-#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_sender.h"
 #include "webrtc/test/testsupport/fileutils.h"
 
 namespace webrtc {
 namespace testing {
 namespace bwe {
 
 class FilterTest : public ::testing::Test {
  public:
@@ skipping 457 matching lines @@
   for (int i = 1; i < kNumElements; ++i) {
     EXPECT_EQ(
         exp_smoothed[i],
         static_cast<int64_t>(exp_smoothed[i - 1] * (1.0f - kAlpha) + 0.5f));
   }
 }
 
 }  // namespace bwe
 }  // namespace testing
 }  // namespace webrtc