Replace NULL with nullptr in all C++ files.

webrtc/tools/frame_analyzer/video_quality_analysis.cc

Index: webrtc/tools/frame_analyzer/video_quality_analysis.cc
diff --git a/webrtc/tools/frame_analyzer/video_quality_analysis.cc b/webrtc/tools/frame_analyzer/video_quality_analysis.cc
index d1b0e314e16ca50e5d06344a36915626c284d1a7..2a0f15556dfc058acbd1a5601a47d8ff96d4837b 100644
--- a/webrtc/tools/frame_analyzer/video_quality_analysis.cc
+++ b/webrtc/tools/frame_analyzer/video_quality_analysis.cc
@@ -53,7 +53,7 @@ int ExtractFrameSequenceNumber(std::string line) {
   }
   std::string frame_number = frame.substr(underscore_position + 1);
 
-  return strtol(frame_number.c_str(), NULL, 10);
+  return strtol(frame_number.c_str(), nullptr, 10);
 }
 
 int ExtractDecodedFrameNumber(std::string line) {
@@ -63,7 +63,7 @@ int ExtractDecodedFrameNumber(std::string line) {
   }
   std::string decoded_number = line.substr(space_position + 1);
 
-  return strtol(decoded_number.c_str(), NULL, 10);
+  return strtol(decoded_number.c_str(), nullptr, 10);
 }
 
 bool IsThereBarcodeError(std::string line) {
@@ -100,7 +100,7 @@ bool ExtractFrameFromYuvFile(const char* i420_file_name,
   bool errors = false;
 
   FILE* input_file = fopen(i420_file_name, "rb");
-  if (input_file == NULL) {
+  if (input_file == nullptr) {
     fprintf(stderr, "Couldn't open input file for reading: %s\n",
             i420_file_name);
     return false;
@@ -130,7 +130,7 @@ bool ExtractFrameFromY4mFile(const char* y4m_file_name,
   int frame_offset = 0;
 
   FILE* input_file = fopen(y4m_file_name, "rb");
-  if (input_file == NULL) {
+  if (input_file == nullptr) {
     fprintf(stderr, "Couldn't open input file for reading: %s\n",
             y4m_file_name);
     return false;
@@ -357,12 +357,12 @@ void PrintMaxRepeatedAndSkippedFrames(FILE* output,
                                       const std::string& stats_file_test_name) {
   FILE* stats_file_ref = fopen(stats_file_ref_name.c_str(), "r");
   FILE* stats_file_test = fopen(stats_file_test_name.c_str(), "r");
-  if (stats_file_ref == NULL) {
+  if (stats_file_ref == nullptr) {
     fprintf(stderr, "Couldn't open reference stats file for reading: %s\n",
             stats_file_ref_name.c_str());
     return;
   }
-  if (stats_file_test == NULL) {
+  if (stats_file_test == nullptr) {
     fprintf(stderr, "Couldn't open test stats file for reading: %s\n",
             stats_file_test_name.c_str());
     fclose(stats_file_ref);