Enable the -Wundef warning for clang

webrtc/modules/audio_processing/agc/agc_manager_direct_unittest.cc

 /*
  *  Copyright (c) 2013 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/audio_processing/agc/agc_manager_direct.h"
 
-#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/common_types.h"
 #include "webrtc/modules/audio_processing/agc/mock_agc.h"
 #include "webrtc/modules/audio_processing/include/mock_audio_processing.h"
 #include "webrtc/system_wrappers/include/trace.h"
 #include "webrtc/test/testsupport/trace_to_stderr.h"
 
 using ::testing::_;
 using ::testing::DoAll;
 using ::testing::Eq;
 using ::testing::Mock;
@@ skipping 652 matching lines @@
   FirstProcess();
 
   EXPECT_CALL(*agc_, GetRmsErrorDb(_))
       .WillRepeatedly(DoAll(SetArgPointee<0>(30), Return(true)));
   volume_.SetMicVolume(0);
   CallProcess(10);
   EXPECT_EQ(0, volume_.GetMicVolume());
 }
 
 }  // namespace webrtc