Enable the -Wundef warning for clang

webrtc/modules/utility/source/process_thread_impl_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 <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/base/task_queue.h"
 #include "webrtc/base/timeutils.h"
 #include "webrtc/modules/include/module.h"
 #include "webrtc/modules/utility/source/process_thread_impl.h"
 
 namespace webrtc {
 
 using ::testing::_;
 using ::testing::DoAll;
 using ::testing::InSequence;
@@ skipping 279 matching lines @@
   ProcessThreadImpl thread("ProcessThread");
   std::unique_ptr<EventWrapper> task_ran(EventWrapper::Create());
   std::unique_ptr<RaiseEventTask> task(new RaiseEventTask(task_ran.get()));
   thread.Start();
   thread.PostTask(std::move(task));
   EXPECT_EQ(kEventSignaled, task_ran->Wait(kEventWaitTimeout));
   thread.Stop();
 }
 
 }  // namespace webrtc