Enable the -Wundef warning for clang

webrtc/modules/remote_bitrate_estimator/test/bwe_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/bwe.h"
 
 #include <vector>
 
-#include "testing/gtest/include/gtest/gtest.h"
+#include "webrtc/test/gtest.h"
 #include "webrtc/base/arraysize.h"
 
 namespace webrtc {
 namespace testing {
 namespace bwe {
 
 const int kSetCapacity = 1000;
 
 class LinkedSetTest : public ::testing::Test {
  public:
@@ skipping 359 matching lines @@
   loss_account = bwe_receiver_.LinkedSetPacketLossRatio();
   EXPECT_NEAR(loss_account.LossRatio(), 0.0f, 0.001f);
 
   // RelieveSetAndUpdateLoss automatically updates loss account.
   EXPECT_NEAR(bwe_receiver_.GlobalReceiverPacketLossRatio(), 0.5f, 0.001f);
 }
 
 }  // namespace bwe
 }  // namespace testing
 }  // namespace webrtc