IDL: Support callback function types in overload resolution

Source/bindings/tests/idls/core/TestObject.idl

 /*
  * Copyright (C) 2013 Google Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions are
  * met:
  *
  *     * Redistributions of source code must retain the above copyright
  * notice, this list of conditions and the following disclaimer.
  *     * Redistributions in binary form must reproduce the above
@@ skipping 430 matching lines @@
     void overloadedMethodF(optional DOMString stringArg);
     void overloadedMethodF(double doubleArg);
     void overloadedMethodG(long longArg);
     void overloadedMethodG(optional TestInterfaceEmpty? testInterfaceEmptyOrNullArg = null);
     void overloadedMethodH(TestInterface testInterfaceArg);
     void overloadedMethodH(TestInterfaceEmpty testInterfaceEmptyArg);
     void overloadedMethodI(DOMString stringArg);
     void overloadedMethodI(double doubleArg);
     void overloadedMethodJ(DOMString stringArg);
     void overloadedMethodJ(TestDictionary testDictionaryArg);
+    void overloadedMethodK(Function functionArg);
+    void overloadedMethodK(DOMString stringArg);
 
     Promise promiseOverloadMethod();
     Promise promiseOverloadMethod(Window arg1, double arg2);
     Promise promiseOverloadMethod(Document arg1, double arg2);
 
     [PerWorldBindings] void overloadedPerWorldBindingsMethod();
     [PerWorldBindings] void overloadedPerWorldBindingsMethod(long longArg);
 
     static void overloadedStaticMethod(long longArg);
     static void overloadedStaticMethod(long longArg1, long longArg2);
@@ skipping 104 matching lines @@
     [ImplementedInPrivateScript] readonly attribute short readonlyShortAttribute;
     [ImplementedInPrivateScript] attribute short shortAttribute;
     [ImplementedInPrivateScript] attribute DOMString stringAttribute;
     [ImplementedInPrivateScript] attribute Node nodeAttribute;
     [OnlyExposedToPrivateScript] short methodImplementedInCPPForPrivateScriptOnly(short value1, short value2);
     [OnlyExposedToPrivateScript] attribute DOMString attributeImplementedInCPPForPrivateScriptOnly;
     [ImplementedInPrivateScript, OnlyExposedToPrivateScript] short methodForPrivateScriptOnly(short value1, short value2);
     [ImplementedInPrivateScript, OnlyExposedToPrivateScript] attribute DOMString attributeForPrivateScriptOnly;
     [ImplementedInPrivateScript] attribute TestEnum enumForPrivateScript;
 };