IDL: Generate union type containers

Source/core/html/HTMLFormControlsCollection.h

Index: Source/core/html/HTMLFormControlsCollection.h
diff --git a/Source/core/html/HTMLFormControlsCollection.h b/Source/core/html/HTMLFormControlsCollection.h
index c8a7c61a24cf731e5cbb85d348bcbd8ce942ad83..4951f8f3224981b21033f312ccfc988183b68500 100644
--- a/Source/core/html/HTMLFormControlsCollection.h
+++ b/Source/core/html/HTMLFormControlsCollection.h
@@ -32,6 +32,7 @@
 namespace blink {
 
 class HTMLImageElement;
+class RadioNodeListOrElement;
 
 // This class is just a big hack to find form elements even in malformed HTML elements.
 // The famous <table><tr><form><td> problem.
@@ -46,7 +47,7 @@ public:
     HTMLElement* item(unsigned offset) const { return toHTMLElement(HTMLCollection::item(offset)); }
 
     virtual HTMLElement* namedItem(const AtomicString& name) const override;
-    void namedGetter(const AtomicString& name, RefPtrWillBeRawPtr<RadioNodeList>&, RefPtrWillBeRawPtr<Element>&);
+    void namedGetter(const AtomicString& name, RadioNodeListOrElement&);
 
     virtual void trace(Visitor*) override;