Make mappedBy lazy.

sdk/lib/core/set.dart

Index: sdk/lib/core/set.dart
diff --git a/sdk/lib/core/set.dart b/sdk/lib/core/set.dart
index 0bcdbb1cd183987b656cd37fa3680d3afd68e4dc..990348c458783d9bdb7f8f94e61cc73a884ffc5e 100644
--- a/sdk/lib/core/set.dart
+++ b/sdk/lib/core/set.dart
@@ -77,7 +77,7 @@ abstract class HashSet<E> extends Set<E> {
 }
 
 
-class _HashSetImpl<E> implements HashSet<E> {
+class _HashSetImpl<E> extends Iterable<E> implements HashSet<E> {
 
   _HashSetImpl() {
     _backingMap = new _HashMapImpl<E, E>();
@@ -145,37 +145,6 @@ class _HashSetImpl<E> implements HashSet<E> {
     });
   }
 
-  Set mappedBy(f(E element)) {
-    Set result = new Set();
-    _backingMap.forEach((E key, E value) {
-      result.add(f(key));
-    });
-    return result;
-  }
-
-  Dynamic reduce(Dynamic initialValue,
-                 Dynamic combine(Dynamic previousValue, E element)) {
-    return Collections.reduce(this, initialValue, combine);
-  }
-
-  Set<E> where(bool f(E element)) {
-    Set<E> result = new Set<E>();
-    _backingMap.forEach((E key, E value) {
-      if (f(key)) result.add(key);
-    });
-    return result;
-  }
-
-  bool every(bool f(E element)) {
-    Collection<E> keys = _backingMap.keys;
-    return keys.every(f);
-  }
-
-  bool some(bool f(E element)) {
-    Collection<E> keys = _backingMap.keys;
-    return keys.some(f);
-  }
-
   bool get isEmpty {
     return _backingMap.isEmpty;
   }
@@ -190,14 +159,6 @@ class _HashSetImpl<E> implements HashSet<E> {
     return Collections.collectionToString(this);
   }
 
-  List<E> toList() {
-    return new List<E>.from(this);
-  }
-
-  Set<E> toSet() {
-    return new Set<E>.from(this);
-  }
-
   // The map backing this set. The associations in this map are all
   // of the form element -> element. If a value is not in the map,
   // then it is not in the set.