Run clang-modernize -use-nullptr over src/extensions/.

extensions/renderer/script_context_set.cc

Index: extensions/renderer/script_context_set.cc
diff --git a/extensions/renderer/script_context_set.cc b/extensions/renderer/script_context_set.cc
index 5ee9db4d2f1a0c69dfcb5c3c17416655facd2df5..cb4da0ed89caf47eaac8aca956f6226824df6c28 100644
--- a/extensions/renderer/script_context_set.cc
+++ b/extensions/renderer/script_context_set.cc
@@ -49,13 +49,13 @@ ScriptContextSet::ContextSet ScriptContextSet::GetAll() const {
 ScriptContext* ScriptContextSet::GetCurrent() const {
   v8::Isolate* isolate = v8::Isolate::GetCurrent();
   return isolate->InContext() ? GetByV8Context(isolate->GetCurrentContext())
-                              : NULL;
+                              : nullptr;
 }
 
 ScriptContext* ScriptContextSet::GetCalling() const {
   v8::Isolate* isolate = v8::Isolate::GetCurrent();
   v8::Local<v8::Context> calling = isolate->GetCallingContext();
-  return calling.IsEmpty() ? NULL : GetByV8Context(calling);
+  return calling.IsEmpty() ? nullptr : GetByV8Context(calling);
 }
 
 ScriptContext* ScriptContextSet::GetByV8Context(
@@ -67,7 +67,7 @@ ScriptContext* ScriptContextSet::GetByV8Context(
       return *iter;
   }
 
-  return NULL;
+  return nullptr;
 }
 
 void ScriptContextSet::ForEach(