Revert "Make EfficientLength public, as EfficientLengthIterable."

sdk/lib/collection/maps.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 dart.collection;
 
 /**
  * Base class for implementing a [Map].
  *
  * This class has a basic implementation of all but five of the members of
@@ skipping 94 matching lines @@
     MapBase<K, V> with _UnmodifiableMapMixin<K, V>;
 
 /**
  * Implementation of [Map.values] based on the map and its [Map.keys] iterable.
  *
  * Iterable that iterates over the values of a `Map`.
  * It accesses the values by iterating over the keys of the map, and using the
  * map's `operator[]` to lookup the keys.
  */
 class _MapBaseValueIterable<V> extends Iterable<V>
-                               implements EfficientLengthIterable<V> {
+                               implements EfficientLength {
   final Map _map;
   _MapBaseValueIterable(this._map);
 
   int get length => _map.length;
   bool get isEmpty => _map.isEmpty;
   bool get isNotEmpty => _map.isNotEmpty;
   V get first => _map[_map.keys.first];
   V get single => _map[_map.keys.single];
   V get last => _map[_map.keys.last];
 
@@ skipping 218 matching lines @@
       map[keyIterator.current] = valueIterator.current;
       hasNextKey = keyIterator.moveNext();
       hasNextValue = valueIterator.moveNext();
     }
 
     if (hasNextKey || hasNextValue) {
       throw new ArgumentError("Iterables do not have same length.");
     }
   }
 }