Remove deprecated Strings class.

tools/dom/templates/html/impl/impl_SVGElement.darttemplate

 // 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.
 
 part of $LIBRARYNAME;
 
 class _AttributeClassSet extends CssClassSet {
   final Element _element;
 
   _AttributeClassSet(this._element);
 
   Set<String> readClasses() {
     var classname = _element.attributes['class'];
 
     Set<String> s = new Set<String>();
     if (classname == null) {
       return s;
     }
     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(' ');
   }
 }
 
 $(ANNOTATIONS)class $CLASSNAME$EXTENDS$IMPLEMENTS$NATIVESPEC {
   factory $CLASSNAME.tag(String tag) =>
       _$(CLASSNAME)FactoryProvider.create$(CLASSNAME)_tag(tag);
   factory $CLASSNAME.svg(String svg) =>
       _$(CLASSNAME)FactoryProvider.create$(CLASSNAME)_svg(svg);
 
   _AttributeClassSet _cssClassSet;
@@ skipping 64 matching lines @@
    * Checks to see if the SVG element type is supported by the current platform.
    *
    * The tag should be a valid SVG element tag name.
    */
   static bool isTagSupported(String tag) {
     var e = new $CLASSNAME.tag(tag);
     return e is $CLASSNAME && !(e is UnknownElement);
   }
 $!MEMBERS
 }