Replace NULL with nullptr in all C++ files.

webrtc/modules/utility/source/helpers_android.cc

Index: webrtc/modules/utility/source/helpers_android.cc
diff --git a/webrtc/modules/utility/source/helpers_android.cc b/webrtc/modules/utility/source/helpers_android.cc
index aea35f8d5a254b34c89bfa855f8129f932ab1847..c19984cb832172b61a30dda8d42d2c72026e59d9 100644
--- a/webrtc/modules/utility/source/helpers_android.cc
+++ b/webrtc/modules/utility/source/helpers_android.cc
@@ -23,10 +23,10 @@
 namespace webrtc {
 
 JNIEnv* GetEnv(JavaVM* jvm) {
-  void* env = NULL;
+  void* env = nullptr;
   jint status = jvm->GetEnv(&env, JNI_VERSION_1_6);
-  RTC_CHECK(((env != NULL) && (status == JNI_OK)) ||
-            ((env == NULL) && (status == JNI_EDETACHED)))
+  RTC_CHECK(((env != nullptr) && (status == JNI_OK)) ||
+            ((env == nullptr) && (status == JNI_EDETACHED)))
       << "Unexpected GetEnv return: " << status << ":" << env;
   return reinterpret_cast<JNIEnv*>(env);
 }
@@ -83,7 +83,7 @@ void DeleteGlobalRef(JNIEnv* jni, jobject o) {
 }
 
 std::string GetThreadId() {
-  char buf[21];  // Big enough to hold a kuint64max plus terminating NULL.
+  char buf[21];  // Big enough to hold a kuint64max plus terminating nullptr.
   int thread_id = gettid();
   RTC_CHECK_LT(snprintf(buf, sizeof(buf), "%i", thread_id),
                static_cast<int>(sizeof(buf)))
@@ -96,14 +96,14 @@ std::string GetThreadInfo() {
 }
 
 AttachThreadScoped::AttachThreadScoped(JavaVM* jvm)
-    : attached_(false), jvm_(jvm), env_(NULL) {
+    : attached_(false), jvm_(jvm), env_(nullptr) {
   env_ = GetEnv(jvm);
   if (!env_) {
     // Adding debug log here so we can track down potential leaks and figure
     // out why we sometimes see "Native thread exiting without having called
     // DetachCurrentThread" in logcat outputs.
     ALOGD("Attaching thread to JVM%s", GetThreadInfo().c_str());
-    jint res = jvm->AttachCurrentThread(&env_, NULL);
+    jint res = jvm->AttachCurrentThread(&env_, nullptr);
     attached_ = (res == JNI_OK);
     RTC_CHECK(attached_) << "AttachCurrentThread failed: " << res;
   }