Enable the -Wundef warning for clang

webrtc/video/vie_remb_unittest.cc

 /*
  *  Copyright (c) 2012 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 <memory>
 #include <vector>
 
-#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/rtp_rtcp/include/rtp_rtcp.h"
 #include "webrtc/modules/rtp_rtcp/mocks/mock_rtp_rtcp.h"
 #include "webrtc/modules/utility/include/mock/mock_process_thread.h"
 #include "webrtc/video/vie_remb.h"
 
 using ::testing::_;
 using ::testing::AnyNumber;
 using ::testing::NiceMock;
 using ::testing::Return;
 
@@ skipping 214 matching lines @@
   vie_remb_->OnReceiveBitrateChanged(ssrcs, bitrate_estimate);
 
   // Lower the estimate to trigger a new packet REMB packet.
   bitrate_estimate = bitrate_estimate - 100;
   EXPECT_CALL(rtp, SetREMBData(_, _))
       .Times(1);
   vie_remb_->OnReceiveBitrateChanged(ssrcs, bitrate_estimate);
 }
 
 }  // namespace webrtc