Remove deprecated Strings class.

sdk/lib/svg/dart2js/svg_dart2js.dart

 library dart.dom.svg;
 
 import 'dart:async';
 import 'dart:collection';
 import 'dart:html';
 import 'dart:html_common';
 import 'dart:_js_helper' show Creates, Returns, JavaScriptIndexingBehavior, JSName;
 import 'dart:_foreign_helper' show JS;
 // DO NOT EDIT
 // Auto-generated dart:svg library.
@@ skipping 5753 matching lines @@
     for (String name in classname.split(' ')) {
       String trimmed = name.trim();
       if (!trimmed.isEmpty) {
         s.add(trimmed);
       }
     }
     return s;
   }
 
   void writeClasses(Set s) {
-    List list = new List.from(s);
-    _element.attributes['class'] = Strings.join(list, ' ');
+    _element.attributes['class'] = s.join(' ');
   }
 }
 
 @DomName('SVGElement')
 class SvgElement extends Element native "*SVGElement" {
   factory SvgElement.tag(String tag) =>
       _SvgElementFactoryProvider.createSvgElement_tag(tag);
   factory SvgElement.svg(String svg) =>
       _SvgElementFactoryProvider.createSvgElement_svg(svg);
 
@@ skipping 1941 matching lines @@
 
 
 @DocsEditable
 @DomName('SVGVKernElement')
 class _SVGVKernElement extends SvgElement native "*SVGVKernElement" {
 
   @DomName('SVGVKernElement.SVGVKernElement')
   @DocsEditable
   factory _SVGVKernElement() => _SvgElementFactoryProvider.createSvgElement_tag("vkern");
 }