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 62dd42703a9c344143a57ae8b1a94adfa4bb3793..78c810af077e31349d42fea52f0d4baf2db82250 100644
--- a/Source/bindings/templates/union.h
+++ b/Source/bindings/templates/union.h
@@ -64,6 +64,21 @@ inline void v8SetReturnValue(const CallbackInfo& callbackInfo, {{container.cpp_c
 }
 
 {% endfor %}
+
+{% for cpp_type in nullable_cpp_types %}
+class V8{{cpp_type}}OrNull final {

[bashi, 2014/11/07 10:07:53]

Maybe "IncludesNull" is accurate, but I'm not sure it sounds fine.

[Jens Widell, 2014/11/07 10:58:19]

"AOrBCommaOrNull" (for "A or B, or null")? ;-)

If we want to avoid the (apparent) ambiguity of whether AOrBOrNull is (A or B?)
or (A or B)?, we could also make it NullOrAOrB.

[haraken, 2014/11/07 18:06:31]

I'm OK with AOrBOrNull :)

[bashi, 2014/11/08 07:10:34]

Let's use "OrNull" suffix :)

+public:
+    static void toImpl(v8::Isolate* isolate, v8::Handle<v8::Value> v8Value, {{cpp_type}}& impl, ExceptionState& exceptionState)
+    {
+        {# http://heycam.github.io/webidl/#es-union #}
+        {# 1. null or undefined #}

[haraken, 2014/11/07 18:06:31]

Can we add unit tests for the following cases?

// IDL
void foo((A or B)? arg);
void bar((A or B) arg);

// JS
foo(null);
foo(undefined);
bar(null);
bar(undefined);

[bashi, 2014/11/08 07:10:34]

Yes, that's what I'm going to add in a follow-up CL.
https://codereview.chromium.org/692993003/

The reason why I didn't include them is that we can only use union types which
are already defined in non-test IDLs. To add layout tests, we need to modify
existing IDL files (HTMLAllCollection in this case). I don't want to includes
such changes in this CL.

+        if (isUndefinedOrNull(v8Value))
+            return;
+        V8{{cpp_type}}::toImpl(isolate, v8Value, impl, exceptionState);
+    }
+};
+
+{% endfor %}
 } // namespace blink
 
 #endif // {{macro_guard}}