Update interfaces/SVG.idl

Note: This file was recently manually updated in commit 5f4cbbb.
      This commit may revert some of those changes.

Source: https://github.com/tidoust/reffy-reports/blob/39f92a5/whatwg/idl/SVG.idl
Build: https://travis-ci.org/tidoust/reffy-reports/builds/447306145

interfaces/SVG.idl

@@ -237,6 +237,14 @@ partial interface Document {
   readonly attribute SVGSVGElement? rootElement;
 };
 
+// must only be implemented in certain implementations
+partial interface Document {
+  readonly attribute DOMString title;
+  readonly attribute DOMString referrer;
+  readonly attribute DOMString domain;
+  readonly attribute Element? activeElement;
+};
+
 [Exposed=Window]
 interface SVGSVGElement : SVGGraphicsElement {