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

samples/swarm/swarm_ui_lib/view/view.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.
 
 library view;
 
 import 'dart:async';
 import 'dart:html';
 import 'dart:math' as Math;
 
@@ skipping 52 matching lines @@
 
     return _node;
   }
 
   /**
    * A subclass that contains child views should override this to return those
    * views. View uses this to ensure that child views are properly rendered
    * and initialized when their parent view is without the parent having to
    * manually handle that traversal.
    */
-  Collection<View> get childViews {
+  Iterable<View> get childViews {
     return const [];
   }
 
   /**
    * View presumes the collection of views returned by childViews is more or
    * less static after the view is first created. Subclasses should call this
    * when that invariant doesn't hold to let View know that a new childView has
    * appeared.
    */
   void childViewAdded(View child) {
@@ skipping 287 matching lines @@
     }
   }
 
   void _applyLayout() {
     if (_layout != null) {
       _layout.applyLayout();
     }
     _applyLayoutToChildren();
   }
 }