Support union return type for anonymous named/indexed getter

Source/bindings/tests/idls/TestObject.idl

 /*
  * Copyright (C) 2009 Google Inc. All rights reserved.
  * Copyright (C) 2010 Apple Inc. All rights reserved.
  *
  * Redistribution and use in source and binary formstrArg, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  *
  * 1.  Redistributions of source code must retain the above copyright
  *     notice, this list of conditions and the following disclaimer.
@@ skipping 71 matching lines @@
     void methodWithSequenceArg(sequence<ScriptProfile> sequenceArg);
     sequence<ScriptProfile> methodReturningSequence(long longArg);
 
     void methodWithEnumArg(TestEnumType enumArg);
     [RaisesException] TestObject methodThatRequiresAllArgsAndThrows(DOMString strArg, TestObject objArg);
 
     void serializedValue(SerializedScriptValue serializedArg);
     void optionsObject(Dictionary oo, optional Dictionary ooo);
 
     // Indexed/named properties
-    [ImplementedAs=item] getter Node (unsigned long index);
+    [ImplementedAs=item] getter (NodeList or Node)(unsigned long index);
     getter DOMString namedItem(DOMString name);
 
     // Exceptions
     [RaisesException] void methodWithException();
     [GetterRaisesException] attribute long attrWithGetterException;
     [SetterRaisesException] attribute long attrWithSetterException;
     [GetterRaisesException] attribute DOMString stringAttrWithGetterException;
     [SetterRaisesException] attribute DOMString stringAttrWithSetterException;
 
     // 'Custom' extended attribute
@@ skipping 195 matching lines @@
     [DeprecateAs=StaticReadonlyAttribute] static readonly attribute long deprecatedStaticReadOnlyAttr;
     [DeprecateAs=StaticAttribute] static attribute long deprecatedStaticAttr;
     [DeprecateAs=ReadonlyAttribute] readonly attribute long deprecatedReadonlyAttr;
     [DeprecateAs=Attribute] attribute long deprecatedAttr;
 
     [DeprecateAs=Method] void deprecatedMethod();
     [DeprecateAs=StaticMethod] static void deprecatedStaticMethod();
 
     [DeprecateAs=Constant] const unsigned short DEPRECATED_CONSTANT = 1;
 };