Replace NULL with nullptr in all C++ files.

webrtc/modules/remote_bitrate_estimator/test/bwe_test_fileutils.cc

Index: webrtc/modules/remote_bitrate_estimator/test/bwe_test_fileutils.cc
diff --git a/webrtc/modules/remote_bitrate_estimator/test/bwe_test_fileutils.cc b/webrtc/modules/remote_bitrate_estimator/test/bwe_test_fileutils.cc
index 5fe78a775898ee44ea5521d1c3c5504629ecdd11..0864269ba88318a3a33dd04f1bd685cbf69e77f4 100644
--- a/webrtc/modules/remote_bitrate_estimator/test/bwe_test_fileutils.cc
+++ b/webrtc/modules/remote_bitrate_estimator/test/bwe_test_fileutils.cc
@@ -25,9 +25,9 @@ namespace testing {
 namespace bwe {
 
 ResourceFileReader::~ResourceFileReader() {
-  if (file_ != NULL) {
+  if (file_ != nullptr) {
     fclose(file_);
-    file_ = NULL;
+    file_ = nullptr;
   }
 }
 
@@ -54,7 +54,7 @@ ResourceFileReader* ResourceFileReader::Create(const std::string& filename,
                                                const std::string& extension) {
   std::string filepath = webrtc::test::ResourcePath(filename, extension);
   FILE* file = fopen(filepath.c_str(), "rb");
-  if (file == NULL) {
+  if (file == nullptr) {
     BWE_TEST_LOGGING_CONTEXT("ResourceFileReader");
     BWE_TEST_LOGGING_LOG1("Create", "Can't read file: %s", filepath.c_str());
     return 0;
@@ -64,9 +64,9 @@ ResourceFileReader* ResourceFileReader::Create(const std::string& filename,
 }
 
 OutputFileWriter::~OutputFileWriter() {
-  if (file_ != NULL) {
+  if (file_ != nullptr) {
     fclose(file_);
-    file_ = NULL;
+    file_ = nullptr;
   }
 }
 
@@ -83,10 +83,10 @@ OutputFileWriter* OutputFileWriter::Create(const std::string& filename,
   std::string filepath = webrtc::test::OutputPath() + filename + "." +
       extension;
   FILE* file = fopen(filepath.c_str(), "wb");
-  if (file == NULL) {
+  if (file == nullptr) {
     BWE_TEST_LOGGING_CONTEXT("OutputFileWriter");
     BWE_TEST_LOGGING_LOG1("Create", "Can't write file: %s", filepath.c_str());
-    return NULL;
+    return nullptr;
   } else {
     return new OutputFileWriter(file);
   }