IDL: make optional arguments (without default) explicit sometimes

Source/core/events/KeyboardEvent.idl

Index: Source/core/events/KeyboardEvent.idl
diff --git a/Source/core/events/KeyboardEvent.idl b/Source/core/events/KeyboardEvent.idl
index ca68d367b11da44762ffd95436da0110eaed41f0..777fa086dea64cc2cc15589f00248d104d4023e9 100644
--- a/Source/core/events/KeyboardEvent.idl
+++ b/Source/core/events/KeyboardEvent.idl
@@ -38,15 +38,15 @@
     boolean getModifierState(DOMString keyArgument);
 
     // FIXME: this does not match the version in the DOM spec.
-    void initKeyboardEvent([Default=Undefined] optional DOMString type,
-                           [Default=Undefined] optional boolean canBubble,
-                           [Default=Undefined] optional boolean cancelable,
-                           [Default=Undefined] optional Window view,
-                           [Default=Undefined] optional DOMString keyIdentifier,
-                           [Default=Undefined] optional unsigned long location,
-                           [Default=Undefined] optional boolean ctrlKey,
-                           [Default=Undefined] optional boolean altKey,
-                           [Default=Undefined] optional boolean shiftKey,
-                           [Default=Undefined] optional boolean metaKey);
+    void initKeyboardEvent(optional DOMString type,
+                           optional boolean canBubble,
+                           optional boolean cancelable,
+                           optional Window view,
+                           optional DOMString keyIdentifier,
+                           optional unsigned long location,
+                           optional boolean ctrlKey,
+                           optional boolean altKey,
+                           optional boolean shiftKey,
+                           optional boolean metaKey);
 };