Remove Collection, Collections and clean up List/Set/Queue implementations of retain/remove.

tools/dom/src/AttributeMap.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;
 
 abstract class _AttributeMap implements Map<String, String> {
   final Element _element;
 
   _AttributeMap(this._element);
@@ skipping 20 matching lines @@
     }
   }
 
   void forEach(void f(String key, String value)) {
     for (var key in keys) {
       var value = this[key];
       f(key, value);
     }
   }
 
-  Collection<String> get keys {
+  Iterable<String> get keys {
     // TODO: generate a lazy collection instead.
     var attributes = _element.$dom_attributes;
     var keys = new List<String>();
     for (int i = 0, len = attributes.length; i < len; i++) {
       if (_matches(attributes[i])) {
         keys.add(attributes[i].localName);
       }
     }
     return keys;
   }
 
-  Collection<String> get values {
+  Iterable<String> get values {
     // TODO: generate a lazy collection instead.
     var attributes = _element.$dom_attributes;
     var values = new List<String>();
     for (int i = 0, len = attributes.length; i < len; i++) {
       if (_matches(attributes[i])) {
         values.add(attributes[i].value);
       }
     }
     return values;
   }
@@ skipping 120 matching lines @@
   }
 
   void forEach(void f(String key, String value)) {
     $dom_attributes.forEach((String key, String value) {
       if (_matches(key)) {
         f(_strip(key), value);
       }
     });
   }
 
-  Collection<String> get keys {
+  Iterable<String> get keys {
     final keys = new List<String>();
     $dom_attributes.forEach((String key, String value) {
       if (_matches(key)) {
         keys.add(_strip(key));
       }
     });
     return keys;
   }
 
-  Collection<String> get values {
+  Iterable<String> get values {
     final values = new List<String>();
     $dom_attributes.forEach((String key, String value) {
       if (_matches(key)) {
         values.add(value);
       }
     });
     return values;
   }
 
   int get length => keys.length;
 
   // TODO: Use lazy iterator when it is available on Map.
   bool get isEmpty => length == 0;
 
   // Helpers.
   String _attr(String key) => 'data-$key';
   bool _matches(String key) => key.startsWith('data-');
   String _strip(String key) => key.substring(5);
 }