Enable the -Wundef warning for clang

webrtc/modules/bitrate_controller/include/mock/mock_bitrate_controller.h

 /*
  *  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.
  */
 
 #ifndef WEBRTC_MODULES_BITRATE_CONTROLLER_INCLUDE_MOCK_MOCK_BITRATE_CONTROLLER_H_
 #define WEBRTC_MODULES_BITRATE_CONTROLLER_INCLUDE_MOCK_MOCK_BITRATE_CONTROLLER_H_
 
-#include "testing/gmock/include/gmock/gmock.h"
+#include "webrtc/test/gmock.h"
 #include "webrtc/modules/bitrate_controller/include/bitrate_controller.h"
 
 namespace webrtc {
 namespace test {
 
 class MockBitrateObserver : public BitrateObserver {
  public:
   MOCK_METHOD3(OnNetworkChanged,
                void(uint32_t bitrate_bps,
                     uint8_t fraction_loss,
@@ skipping 20 matching lines @@
   MOCK_METHOD3(GetNetworkParameters,
                bool(uint32_t* bitrate, uint8_t* fraction_loss, int64_t* rtt));
 
   MOCK_METHOD0(Process, void());
   MOCK_METHOD0(TimeUntilNextProcess, int64_t());
 };
 }  // namespace test
 }  // namespace webrtc
 
 #endif  // WEBRTC_MODULES_BITRATE_CONTROLLER_INCLUDE_MOCK_MOCK_BITRATE_CONTROLLER_H_