Enable the -Wundef warning for clang

webrtc/modules/rtp_rtcp/source/rtcp_packet/report_block_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/modules/rtp_rtcp/source/rtcp_packet/report_block.h"
 
 #include <limits>
 
-#include "testing/gtest/include/gtest/gtest.h"
+#include "webrtc/test/gtest.h"
 #include "webrtc/base/random.h"
 
 using webrtc::rtcp::ReportBlock;
 
 namespace webrtc {
 namespace {
 
 const uint32_t kRemoteSsrc = 0x23456789;
 const uint8_t kFractionLost = 55;
 // Use values that are streamed differently LE and BE.
@@ skipping 51 matching lines @@
 
 TEST(RtcpPacketReportBlockTest, ValidateCumulativeLost) {
   const uint32_t kMaxCumulativeLost = 0xffffff;
   ReportBlock rb;
   EXPECT_FALSE(rb.SetCumulativeLost(kMaxCumulativeLost + 1));
   EXPECT_TRUE(rb.SetCumulativeLost(kMaxCumulativeLost));
 }
 
 }  // namespace
 }  // namespace webrtc