Enable the -Wundef warning for clang

webrtc/test/fake_encoder.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 "webrtc/test/fake_encoder.h"
 
 #include <algorithm>
 
-#include "testing/gtest/include/gtest/gtest.h"
+#include "webrtc/test/gtest.h"
 
 #include "webrtc/base/checks.h"
 #include "webrtc/modules/video_coding/include/video_codec_interface.h"
 #include "webrtc/system_wrappers/include/sleep.h"
 
 namespace webrtc {
 namespace test {
 
 FakeEncoder::FakeEncoder(Clock* clock)
     : clock_(clock),
@@ skipping 180 matching lines @@
       delay_ms_(delay_ms) {}
 
 int32_t DelayedEncoder::Encode(const VideoFrame& input_image,
                                const CodecSpecificInfo* codec_specific_info,
                                const std::vector<FrameType>* frame_types) {
   SleepMs(delay_ms_);
   return FakeEncoder::Encode(input_image, codec_specific_info, frame_types);
 }
 }  // namespace test
 }  // namespace webrtc