Make EfficientLength extend Iterable.

sdk/lib/collection/splay_tree.dart

Index: sdk/lib/collection/splay_tree.dart
diff --git a/sdk/lib/collection/splay_tree.dart b/sdk/lib/collection/splay_tree.dart
index 72a2f5293b90c4c9879b273d24afe07ed9bc9b7d..9a41ef324d2007709f8bb7f74b65dbdca17ee7da 100644
--- a/sdk/lib/collection/splay_tree.dart
+++ b/sdk/lib/collection/splay_tree.dart
@@ -607,8 +607,7 @@ abstract class _SplayTreeIterator<K, T> implements Iterator<T> {
   T _getValue(_SplayTreeNode<K> node);
 }
 
-class _SplayTreeKeyIterable<K> extends Iterable<K>
-                               implements EfficientLength {
+class _SplayTreeKeyIterable<K> extends EfficientLengthIterable<K> {
   _SplayTree<K, _SplayTreeNode<K>> _tree;
   _SplayTreeKeyIterable(this._tree);
   int get length => _tree._count;
@@ -624,8 +623,7 @@ class _SplayTreeKeyIterable<K> extends Iterable<K>
   }
 }
 
-class _SplayTreeValueIterable<K, V> extends Iterable<V>
-                                    implements EfficientLength {
+class _SplayTreeValueIterable<K, V> extends EfficientLengthIterable<V> {
   SplayTreeMap<K, V> _map;
   _SplayTreeValueIterable(this._map);
   int get length => _map._count;