Enable the -Wundef warning for clang

webrtc/modules/audio_device/android/ensure_initialized.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/audio_device/android/ensure_initialized.h"
 
 #include <pthread.h>
 
+#include "webrtc/base/ignore_wundef.h"
+
 // Note: this dependency is dangerous since it reaches into Chromium's base.
 // There's a risk of e.g. macro clashes. This file may only be used in tests.
+RTC_PUSH_IGNORING_WUNDEF()
 #include "base/android/context_utils.h"
 #include "base/android/jni_android.h"
+RTC_POP_IGNORING_WUNDEF()
 #include "webrtc/base/checks.h"
 #include "webrtc/modules/audio_device/android/audio_record_jni.h"
 #include "webrtc/modules/audio_device/android/audio_track_jni.h"
 #include "webrtc/modules/utility/include/jvm_android.h"
 
 namespace webrtc {
 namespace audiodevicemodule {
 
 static pthread_once_t g_initialize_once = PTHREAD_ONCE_INIT;
 
 void EnsureInitializedOnce() {
   RTC_CHECK(::base::android::IsVMInitialized());
   JNIEnv* jni = ::base::android::AttachCurrentThread();
   JavaVM* jvm = NULL;
   RTC_CHECK_EQ(0, jni->GetJavaVM(&jvm));
   jobject context = ::base::android::GetApplicationContext().obj();
 
   // Initialize the Java environment (currently only used by the audio manager).
   webrtc::JVM::Initialize(jvm, context);
 }
 
 void EnsureInitialized() {
   RTC_CHECK_EQ(0, pthread_once(&g_initialize_once, &EnsureInitializedOnce));
 }
 
 }  // namespace audiodevicemodule
 }  // namespace webrtc