Add support for [TreatNullAs] extended attribute for reflected attributes

Source/core/html/HTMLTableRowElement.idl

Index: Source/core/html/HTMLTableRowElement.idl
diff --git a/Source/core/html/HTMLTableRowElement.idl b/Source/core/html/HTMLTableRowElement.idl
index a56f70a46e9e4b279fce95dbb888196066817af7..1b2d27d7a788c929956f373ede2b416665796921 100644
--- a/Source/core/html/HTMLTableRowElement.idl
+++ b/Source/core/html/HTMLTableRowElement.idl
@@ -22,11 +22,11 @@ interface HTMLTableRowElement : HTMLElement {
     readonly attribute long rowIndex;
     readonly attribute long sectionRowIndex;
     readonly attribute HTMLCollection cells;
-    [Reflect] attribute DOMString align;
-    [Reflect] attribute DOMString bgColor;
-    [Reflect=char] attribute DOMString ch;
-    [Reflect=charoff] attribute DOMString chOff;
-    [Reflect] attribute DOMString vAlign;
+    [Reflect, TreatNullAs=NullString] attribute DOMString align;
+    [Reflect, TreatNullAs=NullString] attribute DOMString bgColor;
+    [Reflect=char, TreatNullAs=NullString] attribute DOMString ch;
+    [Reflect=charoff, TreatNullAs=NullString] attribute DOMString chOff;
+    [Reflect, TreatNullAs=NullString] attribute DOMString vAlign;
     [RaisesException] HTMLElement insertCell([Default=Undefined] optional long index);
     [RaisesException] void deleteCell([Default=Undefined] optional long index);
 };