Enable the -Wundef warning for clang

webrtc/common_video/h264/sps_vui_rewriter_unittest.cc

 /*
  *  Copyright (c) 2016 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 <vector>
 
-#include "testing/gtest/include/gtest/gtest.h"
+#include "webrtc/test/gtest.h"
 
 #include "webrtc/base/bitbuffer.h"
 #include "webrtc/base/buffer.h"
 #include "webrtc/base/fileutils.h"
 #include "webrtc/base/logging.h"
 #include "webrtc/base/pathutils.h"
 #include "webrtc/base/stream.h"
 
 #include "webrtc/common_video/h264/sps_vui_rewriter.h"
 #include "webrtc/common_video/h264/h264_common.h"
@@ skipping 161 matching lines @@
              kRewriteRequired_NoVui,
              SpsVuiRewriter::ParseResult::kVuiRewritten);
 REWRITE_TEST(AddBitstreamRestriction,
              kRewriteRequired_NoBitstreamRestriction,
              SpsVuiRewriter::ParseResult::kVuiRewritten);
 REWRITE_TEST(RewriteSuboptimalVui,
              kRewriteRequired_VuiSuboptimal,
              SpsVuiRewriter::ParseResult::kVuiRewritten);
 
 }  // namespace webrtc