Reapply "Convert HashSet, LinkedHashSet to factory methods and custom implementations."

sdk/lib/collection/linked_hash_set.dart

Index: sdk/lib/collection/linked_hash_set.dart
diff --git a/sdk/lib/collection/linked_hash_set.dart b/sdk/lib/collection/linked_hash_set.dart
index 28b7ce26d204cb0e03ca7a317549e2b9ccd14c58..d9aadf2c3e54cf0993cc3d5be433b7883acb42e4 100644
--- a/sdk/lib/collection/linked_hash_set.dart
+++ b/sdk/lib/collection/linked_hash_set.dart
@@ -21,55 +21,13 @@ part of dart.collection;
  * Most simple operations on `HashSet` are done in constant time: [add],
  * [contains], [remove], and [length].
  */
-class LinkedHashSet<E> extends _HashSetBase<E> {
+class LinkedHashSet<E> implements HashSet<E> {
 
-  external LinkedHashSet();
+  external factory LinkedHashSet({ bool equals(E e1, E e2),
+                                   int hashCode(E e),
+                                   bool isValidKey(potentialKey) });
 
   factory LinkedHashSet.from(Iterable<E> iterable) {
     return new LinkedHashSet<E>()..addAll(iterable);
   }
-
-  // Iterable.
-
-  /** Return an iterator that iterates over elements in insertion order. */
-  external Iterator<E> get iterator;
-
-  external int get length;
-
-  external bool get isEmpty;
-
-  external bool get isNotEmpty;
-
-  external bool contains(Object object);
-
-  /** Perform an operation on each element in insertion order. */
-  external void forEach(void action(E element));
-
-  external E get first;
-
-  external E get last;
-
-  E get single {
-    if (length == 1) return first;
-    var message = (length == 0) ? "No Elements" : "Too many elements";
-    throw new StateError(message);
-  }
-
-  // Collection.
-  external void add(E element);
-
-  external void addAll(Iterable<E> objects);
-
-  external bool remove(Object object);
-
-  external void removeAll(Iterable objectsToRemove);
-
-  external void removeWhere(bool test(E element));
-
-  external void retainWhere(bool test(E element));
-
-  external void clear();
-
-  // Set.
-  Set<E> _newSet() => new LinkedHashSet<E>();
 }