Enable the -Wundef warning for clang

webrtc/modules/rtp_rtcp/source/rtcp_packet/extended_jitter_report_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/extended_jitter_report.h"
 
-#include "testing/gmock/include/gmock/gmock.h"
-#include "testing/gtest/include/gtest/gtest.h"
+#include "webrtc/test/gmock.h"
+#include "webrtc/test/gtest.h"
 #include "webrtc/test/rtcp_packet_parser.h"
 
 using testing::ElementsAre;
 using testing::IsEmpty;
 using webrtc::rtcp::ExtendedJitterReport;
 
 namespace webrtc {
 namespace {
 constexpr uint32_t kJitter1 = 0x11121314;
 constexpr uint32_t kJitter2 = 0x22242628;
@@ skipping 42 matching lines @@
 TEST(RtcpPacketExtendedJitterReportTest, ParseFailsWithTooManyItems) {
   ExtendedJitterReport ij;
   ij.SetJitterValues({kJitter1});
   rtc::Buffer raw = ij.Build();
   raw[0]++;  // Damage packet: increase jitter count by 1.
   ExtendedJitterReport parsed;
   EXPECT_FALSE(test::ParseSinglePacket(raw, &parsed));
 }
 
 }  // namespace webrtc