Add support for [TreatNullAs] extended attribute for reflected attributes

Source/core/html/HTMLFrameElement.idl

Index: Source/core/html/HTMLFrameElement.idl
diff --git a/Source/core/html/HTMLFrameElement.idl b/Source/core/html/HTMLFrameElement.idl
index c702fd6951d54014a42d89249ae6089b53fe8d5e..6b9a732a882b284ceda4a63bc00ec3eaecf774ae 100644
--- a/Source/core/html/HTMLFrameElement.idl
+++ b/Source/core/html/HTMLFrameElement.idl
@@ -20,14 +20,14 @@
 
 interface HTMLFrameElement : HTMLElement {
 
-    [Reflect] attribute DOMString frameBorder;
-    [Reflect] attribute DOMString longDesc;
-    [Reflect] attribute DOMString marginHeight;
-    [Reflect] attribute DOMString marginWidth;
-    [Reflect] attribute DOMString name;
+    [Reflect, TreatNullAs=NullString] attribute DOMString frameBorder;
+    [Reflect, TreatNullAs=NullString] attribute DOMString longDesc;
+    [Reflect, TreatNullAs=NullString] attribute DOMString marginHeight;
+    [Reflect, TreatNullAs=NullString] attribute DOMString marginWidth;
+    [Reflect, TreatNullAs=NullString] attribute DOMString name;
     [Reflect] attribute boolean noResize;
-    [Reflect] attribute DOMString scrolling;
-    [Reflect, URL] attribute DOMString src;
+    [Reflect, TreatNullAs=NullString] attribute DOMString scrolling;
+    [Reflect, TreatNullAs=NullString, URL] attribute DOMString src;
 
     // Introduced in DOM Level 2:
     [CheckSecurityForNode] readonly attribute Document contentDocument;