Enable the -Wundef warning for clang

webrtc/modules/desktop_capture/desktop_and_cursor_composer_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/modules/desktop_capture/desktop_and_cursor_composer.h"
 
-#include "testing/gtest/include/gtest/gtest.h"
+#include "webrtc/test/gtest.h"
 #include "webrtc/modules/desktop_capture/desktop_capture_options.h"
 #include "webrtc/modules/desktop_capture/desktop_frame.h"
 #include "webrtc/modules/desktop_capture/mouse_cursor.h"
 #include "webrtc/modules/desktop_capture/shared_desktop_frame.h"
 #include "webrtc/modules/desktop_capture/window_capturer.h"
 #include "webrtc/system_wrappers/include/logging.h"
 
 namespace webrtc {
 
 namespace {
@@ skipping 218 matching lines @@
     // Verify that the cursor is erased before the frame buffer is returned to
     // the screen capturer.
     frame_.reset();
     VerifyFrame(*frame, MouseCursorMonitor::OUTSIDE, DesktopVector());
   }
 }
 
 }  // namespace
 
 }  // namespace webrtc