Enable the -Wundef warning for clang

webrtc/modules/congestion_controller/probe_bitrate_estimator_unittest.cc

 /*
  *  Copyright (c) 2016 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/congestion_controller/probe_bitrate_estimator.h"
 
 #include <vector>
 #include <utility>
 
-#include "testing/gmock/include/gmock/gmock.h"
-#include "testing/gtest/include/gtest/gtest.h"
+#include "webrtc/test/gmock.h"
+#include "webrtc/test/gtest.h"
 #include "webrtc/modules/remote_bitrate_estimator/aimd_rate_control.h"
 
 namespace webrtc {
 
 constexpr int INVALID_BPS = -1;
 
 class TestProbeBitrateEstimator : public ::testing::Test {
  public:
   TestProbeBitrateEstimator() : probe_bitrate_estimator_() {}
 
@@ skipping 108 matching lines @@
 TEST_F(TestProbeBitrateEstimator, IgnoreSizeFirstReceivePacket) {
   AddPacketFeedback(0, 1500, 0, 10);
   AddPacketFeedback(0, 1000, 10, 20);
   AddPacketFeedback(0, 1000, 20, 30);
   AddPacketFeedback(0, 1000, 30, 40);
 
   EXPECT_NEAR(measured_bps_, 800000, 10);
 }
 
 }  // namespace webrtc