Make the VM's dart:core and dart:async library patches clean.

runtime/lib/immutable_map.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.
 // Immutable map class for compiler generated map literals.
 
-class ImmutableMap<K, V> implements Map<K, V> {
+class _ImmutableMap<K, V> implements Map<K, V> {
   final _ImmutableList _kvPairs;
 
-  const ImmutableMap._create(_ImmutableList keyValuePairs)
+  const _ImmutableMap._create(_ImmutableList keyValuePairs)
       : _kvPairs = keyValuePairs;
 
 
   V operator [](Object key) {
     // To preserve the key-value order of the map literal, the keys are
     // not sorted. Need to do linear search or implement an additional
     // lookup table.
     for (int i = 0; i < _kvPairs.length - 1; i += 2) {
       if (key == _kvPairs[i]) {
         return _kvPairs[i+1];
@@ skipping 59 matching lines @@
   V remove(Object key) {
     throw new UnsupportedError("Cannot remove from unmodifiable Map");
   }
 
   String toString() {
     return Maps.mapToString(this);
   }
 }
 
 class _ImmutableMapKeyIterable<E> extends EfficientLengthIterable<E> {
-  final ImmutableMap _map;
+  final _ImmutableMap _map;
   _ImmutableMapKeyIterable(this._map);
 
   Iterator<E> get iterator {
     return new _ImmutableMapKeyIterator<E>(_map);
   }
 
   int get length => _map.length;
 }
 
 class _ImmutableMapValueIterable<E> extends EfficientLengthIterable<E> {
-  final ImmutableMap _map;
+  final _ImmutableMap _map;
   _ImmutableMapValueIterable(this._map);
 
   Iterator<E> get iterator {
     return new _ImmutableMapValueIterator<E>(_map);
   }
 
   int get length => _map.length;
 }
 
 class _ImmutableMapKeyIterator<E> implements Iterator<E> {
-  ImmutableMap _map;
+  _ImmutableMap _map;
   int _index = -1;
   E _current;
 
   _ImmutableMapKeyIterator(this._map);
 
   bool moveNext() {
     int newIndex = _index + 1;
     if (newIndex < _map.length) {
       _index = newIndex;
       _current = _map._kvPairs[newIndex * 2];
       return true;
     }
     _current = null;
     _index = _map.length;
     return false;
   }
 
   E get current => _current;
 }
 
 class _ImmutableMapValueIterator<E> implements Iterator<E> {
-  ImmutableMap _map;
+  _ImmutableMap _map;
   int _index = -1;
   E _current;
 
   _ImmutableMapValueIterator(this._map);
 
   bool moveNext() {
     int newIndex = _index + 1;
     if (newIndex < _map.length) {
       _index = newIndex;
       _current = _map._kvPairs[newIndex * 2 + 1];
       return true;
     }
     _current = null;
     _index = _map.length;
     return false;
   }
 
   E get current => _current;
 }