Enable the -Wundef warning for clang

webrtc/common_video/h264/pps_parser_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 "webrtc/common_video/h264/pps_parser.h"
 
 #include <limits>
 #include <memory>
 
-#include "testing/gtest/include/gtest/gtest.h"
+#include "webrtc/test/gtest.h"
 
 #include "webrtc/base/bitbuffer.h"
 #include "webrtc/base/buffer.h"
 #include "webrtc/common_video/h264/h264_common.h"
 
 namespace webrtc {
 
 namespace {
 // Contains enough of the image slice to contain slice QP.
 const uint8_t kH264BitstreamChunk[] = {
@@ skipping 186 matching lines @@
 }
 
 TEST_F(PpsParserTest, PpsIdFromSlice) {
   rtc::Optional<uint32_t> pps_id = PpsParser::ParsePpsIdFromSlice(
       kH264BitstreamChunk, sizeof(kH264BitstreamChunk));
   ASSERT_TRUE(pps_id);
   EXPECT_EQ(2u, *pps_id);
 }
 
 }  // namespace webrtc