IDL: make optional arguments (without default) explicit sometimes

Source/core/xml/DocumentXPathEvaluator.idl

Index: Source/core/xml/DocumentXPathEvaluator.idl
diff --git a/Source/core/xml/DocumentXPathEvaluator.idl b/Source/core/xml/DocumentXPathEvaluator.idl
index 8380ad0f4bf31f653c08d5eace91945bd79ef9a4..9f0d20e38e12b0f92ee3c8d93a1b29bdd53b9ff3 100644
--- a/Source/core/xml/DocumentXPathEvaluator.idl
+++ b/Source/core/xml/DocumentXPathEvaluator.idl
@@ -19,12 +19,12 @@
 
 partial interface Document {
     // DOM Level 3 XPath (XPathEvaluator interface)
-    [MeasureAs=DocumentXPathCreateExpression, RaisesException] XPathExpression createExpression([Default=Undefined] optional DOMString expression,
-                                                       [Default=Undefined] optional XPathNSResolver resolver);
+    [MeasureAs=DocumentXPathCreateExpression, RaisesException] XPathExpression createExpression(optional DOMString expression,
+                                                       optional XPathNSResolver resolver);
     [MeasureAs=DocumentXPathCreateNSResolver] XPathNSResolver    createNSResolver(Node nodeResolver);
-    [Custom, MeasureAs=DocumentXPathEvaluate, RaisesException] XPathResult evaluate([Default=Undefined] optional DOMString expression,
-                                                   [Default=Undefined] optional Node contextNode,
-                                                   [Default=Undefined] optional XPathNSResolver resolver,
-                                                   [Default=Undefined] optional unsigned short type,
-                                                   [Default=Undefined] optional XPathResult inResult);
+    [Custom, MeasureAs=DocumentXPathEvaluate, RaisesException] XPathResult evaluate(optional DOMString expression,
+                                                   optional Node contextNode,
+                                                   optional XPathNSResolver resolver,
+                                                   optional unsigned short type,
+                                                   optional XPathResult inResult);
 };