Remove meaningless uses of [TypeChecking=Nullable]

Source/core/dom/Element.idl

Index: Source/core/dom/Element.idl
diff --git a/Source/core/dom/Element.idl b/Source/core/dom/Element.idl
index 666b01cdbe68b1e1c501ce1f79685b8e4006c63d..62015ef287c7dc4e2c75c6758d1781212697969a 100644
--- a/Source/core/dom/Element.idl
+++ b/Source/core/dom/Element.idl
@@ -30,8 +30,8 @@
     [RaisesException, CustomElementCallbacks] void setAttribute(DOMString name, DOMString value);
     [CustomElementCallbacks] void removeAttribute(DOMString name);
     [MeasureAs=ElementGetAttributeNode] Attr getAttributeNode([Default=Undefined] optional DOMString name); // Removed from DOM4.
-    [RaisesException, CustomElementCallbacks, MeasureAs=ElementSetAttributeNode] Attr setAttributeNode([Default=Undefined, TypeChecking=Nullable] optional Attr newAttr); // Removed from DOM4.
-    [RaisesException, CustomElementCallbacks, MeasureAs=ElementRemoveAttributeNode] Attr removeAttributeNode([Default=Undefined, TypeChecking=Nullable] optional Attr oldAttr); // Removed from DOM4.
+    [RaisesException, CustomElementCallbacks, MeasureAs=ElementSetAttributeNode] Attr setAttributeNode([Default=Undefined] optional Attr newAttr); // Removed from DOM4.
+    [RaisesException, CustomElementCallbacks, MeasureAs=ElementRemoveAttributeNode] Attr removeAttributeNode([Default=Undefined] optional Attr oldAttr); // Removed from DOM4.
     HTMLCollection getElementsByTagName(DOMString name);
 
     [PerWorldBindings, ImplementedAs=attributesForBindings] readonly attribute NamedNodeMap     attributes;
@@ -45,7 +45,7 @@
     HTMLCollection getElementsByTagNameNS([TreatNullAs=NullString] DOMString namespaceURI, DOMString localName);
     [MeasureAs=ElementGetAttributeNodeNS] Attr getAttributeNodeNS([TreatNullAs=NullString, Default=Undefined] optional DOMString namespaceURI,
                                                                   [Default=Undefined] optional DOMString localName); // Removed from DOM4.
-    [RaisesException, CustomElementCallbacks, DeprecateAs=ElementSetAttributeNodeNS] Attr setAttributeNodeNS([Default=Undefined, TypeChecking=Nullable] optional Attr newAttr); // Removed from DOM4.
+    [RaisesException, CustomElementCallbacks, DeprecateAs=ElementSetAttributeNodeNS] Attr setAttributeNodeNS([Default=Undefined] optional Attr newAttr); // Removed from DOM4.
     boolean hasAttribute(DOMString name);
     boolean hasAttributeNS([TreatNullAs=NullString] DOMString namespaceURI, DOMString localName);