Enable the -Wundef warning for clang

webrtc/modules/module_common_types_unittest.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/modules/include/module_common_types.h"
 
-#include "testing/gtest/include/gtest/gtest.h"
+#include "webrtc/test/gtest.h"
 
 namespace webrtc {
 
 TEST(IsNewerSequenceNumber, Equal) {
   EXPECT_FALSE(IsNewerSequenceNumber(0x0001, 0x0001));
 }
 
 TEST(IsNewerSequenceNumber, NoWrap) {
   EXPECT_TRUE(IsNewerSequenceNumber(0xFFFF, 0xFFFE));
   EXPECT_TRUE(IsNewerSequenceNumber(0x0001, 0x0000));
@@ skipping 151 matching lines @@
 
   seq = kNumWraps * 0xFFFF;
   unwrapper.UpdateLast(seq);
   for (; seq >= 0; --seq) {
     int64_t unwrapped = unwrapper.Unwrap(static_cast<uint16_t>(seq & 0xFFFF));
     EXPECT_EQ(seq, unwrapped);
   }
 }
 
 }  // namespace webrtc