[SVG2] Make ownerSVGElement and viewportElement nullable.

Source/core/svg/SVGElement.idl

Index: Source/core/svg/SVGElement.idl
diff --git a/Source/core/svg/SVGElement.idl b/Source/core/svg/SVGElement.idl
index 8ce9e7d0cdeddaaf537d4f488a009bc8e383571d..d18904f64126c1e08b4cb815a3abcb6cb18eca56 100644
--- a/Source/core/svg/SVGElement.idl
+++ b/Source/core/svg/SVGElement.idl
@@ -24,8 +24,8 @@
     Custom=Wrap,
 ] interface SVGElement : Element {
     attribute DOMString xmlbase;
-    readonly attribute SVGSVGElement ownerSVGElement;
-    readonly attribute SVGElement viewportElement;
+    [TypeChecking=Interface|Nullable] readonly attribute SVGSVGElement? ownerSVGElement;
+    [TypeChecking=Interface|Nullable] readonly attribute SVGElement? viewportElement;

[fs, 2014/05/26 13:05:42]

Note: This extended attribute will not "do anything" in this case (because of
the readonly - i.e. no setter), but it makes sense to add it nonetheless (IMHO).

[Erik Dahlström (inactive), 2014/05/26 13:13:35]

I followed the lead from HTMLMediaElement.idl, which had the same. I'll leave it
as is.

 
     attribute DOMString xmllang;
     attribute DOMString xmlspace;