Make EventListener a callback interface

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 37 matching lines @@
     attribute TestEnumType             enumAttr;
     readonly attribute TestEnumType    readOnlyEnumAttr;
     attribute byte                     byteAttr;
     attribute octet                    octetAttr;
     attribute short                    shortAttr;
     attribute unsigned short           unsignedShortAttr;
     attribute long                     longAttr;
     attribute long long                longLongAttr;
     attribute unsigned long long       unsignedLongLongAttr;
     attribute DOMString                stringAttr;
+    attribute EventListener            eventListenerAttr;
     [MeasureAs=TestFeature] attribute TestObject testObjAttr;
 
     // WK_ucfirst, WK_lcfirst exceptional cases.
     attribute TestObject                  XMLObjAttr;
     attribute boolean                  create;
 
     // Reflected DOM attributes
     [Reflect] attribute DOMString reflectedStringAttr;
     [Reflect] attribute long reflectedIntegralAttr;
     [Reflect] attribute unsigned long reflectedUnsignedIntegralAttr;
@@ skipping 249 matching lines @@
 
     [DeprecateAs=Method] void deprecatedMethod();
     [DeprecateAs=StaticMethod] static void deprecatedStaticMethod();
 
     [DeprecateAs=Constant] const unsigned short DEPRECATED_CONSTANT = 1;
 };
 
 // The following comment should not generate any code
 // TestObject implements TestImplements;