IDL: make optional arguments (without default) explicit sometimes

Source/core/inspector/JavaScriptCallFrame.idl

 /*
  * Copyright (C) 2008 Apple 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:
  * 1. Redistributions of source code must retain the above copyright
  *    notice, this list of conditions and the following disclaimer.
  * 2. Redistributions in binary form must reproduce the above copyright
  *    notice, this list of conditions and the following disclaimer in the
@@ skipping 22 matching lines @@
     const unsigned short GLOBAL_SCOPE = 0;
     const unsigned short LOCAL_SCOPE = 1;
     const unsigned short WITH_SCOPE = 2;
     const unsigned short CLOSURE_SCOPE = 3;
     const unsigned short CATCH_SCOPE = 4;
 
     [Custom] void evaluateWithExceptionDetails(DOMString script);
     [Custom] any restart();
 
     // Only declarative scope (local, with and catch) is accepted. Returns undefined.
-    [CallWith=ScriptState] any setVariableValue([Default=Undefined] optional long scopeIndex, [TreatUndefinedAs=NullString, Default=Undefined] optional DOMString? variableName, [Default=Undefined] optional any newValue);
+    [CallWith=ScriptState] any setVariableValue(optional long scopeIndex, [TreatUndefinedAs=NullString] optional DOMString? variableName, optional any newValue);
 
     readonly attribute JavaScriptCallFrame caller;
     readonly attribute long sourceID;
     readonly attribute long line;
     readonly attribute long column;
     [Custom=Getter] readonly attribute object scopeChain;
     [Custom] unsigned short scopeType(long scopeIndex);
     [Custom=Getter] readonly attribute object thisObject;
     readonly attribute DOMString stepInPositions;
     readonly attribute DOMString functionName;
     [Custom=Getter] readonly attribute DOMString type;
     readonly attribute boolean isAtReturn;
     [Custom=Getter] readonly attribute any returnValue;
 };