Enable the -Wundef warning for clang

webrtc/modules/audio_processing/audio_processing_unittest.cc

Index: webrtc/modules/audio_processing/audio_processing_unittest.cc
diff --git a/webrtc/modules/audio_processing/audio_processing_unittest.cc b/webrtc/modules/audio_processing/audio_processing_unittest.cc
index 646e8b7b874eb1c0baba34c12cb926503d3a5d1a..ce18d6dbf0c0c21f416e8f2a4ad3c4d9166f9c47 100644
--- a/webrtc/modules/audio_processing/audio_processing_unittest.cc
+++ b/webrtc/modules/audio_processing/audio_processing_unittest.cc
@@ -18,6 +18,8 @@
 
 #include "webrtc/base/arraysize.h"
 #include "webrtc/base/checks.h"
+#include "webrtc/base/gtest.h"
+#include "webrtc/base/ignore_wundef.h"
 #include "webrtc/common_audio/include/audio_util.h"
 #include "webrtc/common_audio/resampler/include/push_resampler.h"
 #include "webrtc/common_audio/resampler/push_sinc_resampler.h"
@@ -31,13 +33,14 @@
 #include "webrtc/system_wrappers/include/event_wrapper.h"
 #include "webrtc/system_wrappers/include/trace.h"
 #include "webrtc/test/testsupport/fileutils.h"
+
+RTC_PUSH_IGNORING_WUNDEF()
 #ifdef WEBRTC_ANDROID_PLATFORM_BUILD
-#include "gtest/gtest.h"
 #include "external/webrtc/webrtc/modules/audio_processing/test/unittest.pb.h"
 #else
-#include "testing/gtest/include/gtest/gtest.h"
 #include "webrtc/modules/audio_processing/unittest.pb.h"
 #endif
+RTC_POP_IGNORING_WUNDEF()
 
 namespace webrtc {
 namespace {