Add a couple useful SVG constructors.

client/html/src/SVGElementWrappingImplementation.dart

 // Copyright (c) 2011, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
-// WARNING: Do not edit - generated code.
-
 class SVGElementWrappingImplementation extends ElementWrappingImplementation implements SVGElement {
   SVGElementWrappingImplementation._wrap(ptr) : super._wrap(ptr) {}
 
+  factory SVGElementWrappingImplementation.tag(String tag) =>
+    LevelDom.wrapSVGElement(dom.document.createElementNS(
+        "http://www.w3.org/2000/svg", tag));
+
   String get id() { return _ptr.id; }
 
   void set id(String value) { _ptr.id = value; }
 
   SVGSVGElement get ownerSVGElement() { return LevelDom.wrapSVGSVGElement(_ptr.ownerSVGElement); }
 
   SVGElement get viewportElement() { return LevelDom.wrapSVGElement(_ptr.viewportElement); }
 
   String get xmlbase() { return _ptr.xmlbase; }
 
   void set xmlbase(String value) { _ptr.xmlbase = value; }
 }