Replace NULL with nullptr in all C++ files.

webrtc/system_wrappers/source/event_timer_win.cc

Index: webrtc/system_wrappers/source/event_timer_win.cc
diff --git a/webrtc/system_wrappers/source/event_timer_win.cc b/webrtc/system_wrappers/source/event_timer_win.cc
index 4c586988df65af8dff43721eee9aaae06104b776..9908a20a6a8ccfd451fc33378fdf673db7f2490e 100644
--- a/webrtc/system_wrappers/source/event_timer_win.cc
+++ b/webrtc/system_wrappers/source/event_timer_win.cc
@@ -20,12 +20,11 @@ EventTimerWrapper* EventTimerWrapper::Create() {
 }
 
 EventTimerWin::EventTimerWin()
-    : event_(::CreateEvent(NULL,    // security attributes
-                           FALSE,   // manual reset
-                           FALSE,   // initial state
-                           NULL)),  // name of event
-    timerID_(NULL) {
-}
+    : event_(::CreateEvent(nullptr,    // security attributes
+                           FALSE,      // manual reset
+                           FALSE,      // initial state
+                           nullptr)),  // name of event
+      timerID_(nullptr) {}
 
 EventTimerWin::~EventTimerWin() {
   StopTimer();
@@ -50,9 +49,9 @@ EventTypeWrapper EventTimerWin::Wait(unsigned long max_time) {
 }
 
 bool EventTimerWin::StartTimer(bool periodic, unsigned long time) {
-  if (timerID_ != NULL) {
+  if (timerID_ != nullptr) {
     timeKillEvent(timerID_);
-    timerID_ = NULL;
+    timerID_ = nullptr;
   }
 
   if (periodic) {
@@ -63,13 +62,13 @@ bool EventTimerWin::StartTimer(bool periodic, unsigned long time) {
                             TIME_ONESHOT | TIME_CALLBACK_EVENT_SET);
   }
 
-  return timerID_ != NULL;
+  return timerID_ != nullptr;
 }
 
 bool EventTimerWin::StopTimer() {
-  if (timerID_ != NULL) {
+  if (timerID_ != nullptr) {
     timeKillEvent(timerID_);
-    timerID_ = NULL;
+    timerID_ = nullptr;
   }
 
   return true;