Replace NULL with nullptr or null in webrtc/base/.

webrtc/base/trace_event.h

Index: webrtc/base/trace_event.h
diff --git a/webrtc/base/trace_event.h b/webrtc/base/trace_event.h
index 3916af4fb61bf713139f60f617c02793b24ade3e..bca885cb56cf9fff2430dc02d7c9726e7b85e158 100644
--- a/webrtc/base/trace_event.h
+++ b/webrtc/base/trace_event.h
@@ -820,10 +820,9 @@ static inline void AddTraceEvent(char phase,
                                 const char* name,
                                 unsigned long long id,
                                 unsigned char flags) {
-  TRACE_EVENT_API_ADD_TRACE_EVENT(
-      phase, category_enabled, name, id,
-      kZeroNumArgs, NULL, NULL, NULL,
-      flags);
+  TRACE_EVENT_API_ADD_TRACE_EVENT(phase, category_enabled, name, id,
+                                  kZeroNumArgs, nullptr, nullptr, nullptr,
+                                  flags);
 }
 
 template<class ARG1_TYPE>
@@ -870,7 +869,7 @@ static inline void AddTraceEvent(char phase,
 class TraceEndOnScopeClose {
  public:
   // Note: members of data_ intentionally left uninitialized. See Initialize.
-  TraceEndOnScopeClose() : p_data_(NULL) {}
+  TraceEndOnScopeClose() : p_data_(nullptr) {}
   ~TraceEndOnScopeClose() {
     if (p_data_)
       AddEventIfEnabled();
@@ -888,12 +887,10 @@ class TraceEndOnScopeClose {
   void AddEventIfEnabled() {
     // Only called when p_data_ is non-null.
     if (*p_data_->category_enabled) {
-      TRACE_EVENT_API_ADD_TRACE_EVENT(
-          TRACE_EVENT_PHASE_END,
-          p_data_->category_enabled,
-          p_data_->name, kNoEventId,
-          kZeroNumArgs, NULL, NULL, NULL,
-          TRACE_EVENT_FLAG_NONE);
+      TRACE_EVENT_API_ADD_TRACE_EVENT(TRACE_EVENT_PHASE_END,
+                                      p_data_->category_enabled, p_data_->name,
+                                      kNoEventId, kZeroNumArgs, nullptr,
+                                      nullptr, nullptr, TRACE_EVENT_FLAG_NONE);
     }
   }