Add type annotations to some dart:html closures

sdk/lib/html/html_common/css_class_set.dart

 // Copyright (c) 2012, 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 html_common;
 
 abstract class CssClassSetImpl implements CssClassSet {
 
   String toString() {
     return readClasses().join(' ');
@@ skipping 175 matching lines @@
       readClasses().skipWhile(test);
   String firstWhere(bool test(String value), { String orElse() }) =>
       readClasses().firstWhere(test, orElse: orElse);
   String lastWhere(bool test(String value), { String orElse()}) =>
       readClasses().lastWhere(test, orElse: orElse);
   String singleWhere(bool test(String value)) =>
       readClasses().singleWhere(test);
   String elementAt(int index) => readClasses().elementAt(index);
 
   void clear() {
+    // TODO(sra): Do this without reading the classes.
     modify((s) => s.clear());
   }
   // interface Set - END
 
   /**
    * Helper method used to modify the set of css classes on this element.
    *
    *   f - callback with:
    *   s - a Set of all the css class name currently on this element.
    *
@@ skipping 14 matching lines @@
    */
   Set<String> readClasses();
 
   /**
    * Join all the elements of a set into one string and write
    * back to the element.
    * This is intended to be overridden by specific implementations.
    */
   void writeClasses(Set<String> s);
 }