IDL union: nullable support

Source/bindings/templates/union.h

Index: Source/bindings/templates/union.h
diff --git a/Source/bindings/templates/union.h b/Source/bindings/templates/union.h
index 5cb527951b64f2bd57521e9ba4f9a7b47b41dc2e..54a913d985fcddac528948ad25fd06f1a17b3407 100644
--- a/Source/bindings/templates/union.h
+++ b/Source/bindings/templates/union.h
@@ -62,6 +62,21 @@ inline void v8SetReturnValue(const CallbackInfo& callbackInfo, {{container.cpp_c
 }
 
 {% endfor %}
+
+{% for nullable_container in nullable_containers %}
+class V8{{nullable_container.cpp_class}}OrNull final {
+public:
+    static void toImpl(v8::Isolate* isolate, v8::Handle<v8::Value> v8Value, {{nullable_container.cpp_class}}& impl, ExceptionState& exceptionState)
+    {
+        {# http://heycam.github.io/webidl/#es-union #}
+        {# 1. null or undefined #}
+        if (isUndefinedOrNull(v8Value))
+            return;
+        V8{{nullable_container.cpp_class}}::toImpl(isolate, v8Value, impl, exceptionState);
+    }
+};
+
+{% endfor %}
 } // namespace blink
 
 #endif // {{macro_guard}}