Enable the -Wundef warning for clang

webrtc/common_video/h264/sps_parser_unittest.cc

 /*
  *  Copyright (c) 2015 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 "webrtc/common_video/h264/sps_parser.h"
 
-#include "testing/gtest/include/gtest/gtest.h"
+#include "webrtc/test/gtest.h"
 
 #include "webrtc/base/arraysize.h"
 #include "webrtc/base/bitbuffer.h"
 #include "webrtc/base/buffer.h"
 #include "webrtc/common_video/h264/h264_common.h"
 
 namespace webrtc {
 
 // Example SPS can be generated with ffmpeg. Here's an example set of commands,
 // runnable on OS X:
@@ skipping 142 matching lines @@
   rtc::Buffer buffer;
   GenerateFakeSps(156u, 122u, 2, &buffer);
   EXPECT_TRUE(static_cast<bool>(
       sps_ = SpsParser::ParseSps(buffer.data(), buffer.size())));
   EXPECT_EQ(156u, sps_->width);
   EXPECT_EQ(122u, sps_->height);
   EXPECT_EQ(2u, sps_->id);
 }
 
 }  // namespace webrtc