Enable the -Wundef warning for clang

webrtc/base/thread_checker_unittest.cc

 /*
  *  Copyright (c) 2014 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.
  */
 
 // Borrowed from Chromium's src/base/threading/thread_checker_unittest.cc.
 
 #include <memory>
 
-#include "testing/gtest/include/gtest/gtest.h"
+#include "webrtc/base/gtest.h"

[kjellander_webrtc, 2016/09/23 12:32:36]

sort

 #include "webrtc/base/checks.h"
 #include "webrtc/base/constructormagic.h"
 #include "webrtc/base/task_queue.h"
 #include "webrtc/base/thread.h"
 #include "webrtc/base/thread_checker.h"
 
 // Duplicated from base/threading/thread_checker.h so that we can be
 // good citizens there and undef the macro.
 #if !defined(NDEBUG) || defined(DCHECK_ALWAYS_ON)
 #define ENABLE_THREAD_CHECKER 1
@@ skipping 221 matching lines @@
 
   int var_thread_ ACCESS_ON(thread_);
   int var_checker_ GUARDED_BY(checker_);
   int var_queue_ ACCESS_ON(queue_);
 };
 
 // Just in case we ever get lumped together with other compilation units.
 #undef ENABLE_THREAD_CHECKER
 
 }  // namespace rtc