Use nullptr_t for RefPtr, PassRefPtr and RawPtr.

Source/bindings/v8/ScriptCallStackFactory.cpp

Index: Source/bindings/v8/ScriptCallStackFactory.cpp
diff --git a/Source/bindings/v8/ScriptCallStackFactory.cpp b/Source/bindings/v8/ScriptCallStackFactory.cpp
index e1d531c4918e688adf6b3e8d8e646601c695d98e..51ce9b2b20abd77bf4f0e5c9f653b435cdbbc62e 100644
--- a/Source/bindings/v8/ScriptCallStackFactory.cpp
+++ b/Source/bindings/v8/ScriptCallStackFactory.cpp
@@ -104,7 +104,7 @@ PassRefPtr<ScriptCallStack> createScriptCallStack(size_t maxStackSize, bool empt
 {
     v8::Isolate* isolate = v8::Isolate::GetCurrent();
     if (!isolate->InContext())
-        return 0;
+        return nullptr;
     v8::HandleScope handleScope(isolate);
     v8::Handle<v8::StackTrace> stackTrace(v8::StackTrace::CurrentStackTrace(isolate, maxStackSize, stackTraceOptions));
     return createScriptCallStack(stackTrace, maxStackSize, emptyStackIsAllowed, isolate);