Enable the -Wundef warning for clang

webrtc/video/overuse_frame_detector_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 <memory>
 
 #include "webrtc/video/overuse_frame_detector.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/base/event.h"
 #include "webrtc/system_wrappers/include/clock.h"
 #include "webrtc/video_frame.h"
 
 namespace webrtc {
 
 using ::testing::Invoke;
 
 namespace {
@@ skipping 319 matching lines @@
     InsertAndSendFramesWithInterval(1300, kFrameInterval33ms, kWidth, kHeight,
                                     kDelayMs1);
     InsertAndSendFramesWithInterval(1, kFrameInterval33ms, kWidth, kHeight,
                                     kDelayMs2);
   });
 
   EXPECT_TRUE(event.Wait(10000));
 }
 
 }  // namespace webrtc