Add SetBase/SetMixin.

sdk/lib/_internal/lib/collection_patch.dart

Index: sdk/lib/_internal/lib/collection_patch.dart
diff --git a/sdk/lib/_internal/lib/collection_patch.dart b/sdk/lib/_internal/lib/collection_patch.dart
index 463fab9c4cb24ca2a7f4e62af549ed2dc1c6134d..1cccb421759554332330a7deb87d5111812b9893 100644
--- a/sdk/lib/_internal/lib/collection_patch.dart
+++ b/sdk/lib/_internal/lib/collection_patch.dart
@@ -992,7 +992,7 @@ patch class HashSet<E> {
   patch factory HashSet.identity() = _IdentityHashSet<E>;
 }
 
-class _HashSet<E> extends _HashSetBase<E> implements HashSet<E> {
+class _HashSet<E> extends SetBase<E> implements HashSet<E> {
   int _length = 0;
 
   // The hash set contents are divided into three parts: one part for
@@ -1016,7 +1016,7 @@ class _HashSet<E> extends _HashSetBase<E> implements HashSet<E> {
 
   _HashSet();
 
-  Set<E> _newSet() => new _HashSet<E>();
+  Set<E> cloneEmpty() => new _HashSet<E>();
 
   // Iterable.
   Iterator<E> get iterator {
@@ -1126,24 +1126,6 @@ class _HashSet<E> extends _HashSetBase<E> implements HashSet<E> {
     return true;
   }
 
-  void removeAll(Iterable<Object> objectsToRemove) {
-    for (var each in objectsToRemove) {
-      remove(each);
-    }
-  }
-
-  void retainAll(Iterable<Object> elements) {
-    super._retainAll(elements, (o) => o is E);
-  }
-
-  void removeWhere(bool test(E element)) {
-    removeAll(_computeElements().where(test));
-  }
-
-  void retainWhere(bool test(E element)) {
-    removeAll(_computeElements().where((E element) => !test(element)));
-  }
-
   void clear() {
     if (_length > 0) {
       _strings = _nums = _rest = _elements = null;
@@ -1286,7 +1268,7 @@ class _HashSet<E> extends _HashSetBase<E> implements HashSet<E> {
 }
 
 class _IdentityHashSet<E> extends _HashSet<E> {
-  Set<E> _newSet() => new _IdentityHashSet<E>();
+  Set<E> cloneEmpty() => new _IdentityHashSet<E>();
 
   int _computeHashCode(var key) {
     // We force the hash codes to be unsigned 30-bit integers to avoid
@@ -1312,7 +1294,7 @@ class _CustomHashSet<E> extends _HashSet<E> {
   _CustomHashSet(this._equality, this._hasher, bool validKey(potentialKey))
       : _validKey = (validKey != null) ? validKey : ((x) => x is E);
 
-  Set<E> _newSet() => new _CustomHashSet<E>(_equality, _hasher, _validKey);
+  Set<E> cloneEmpty() => new _CustomHashSet<E>(_equality, _hasher, _validKey);
 
   int _findBucketIndex(var bucket, var element) {
     if (bucket == null) return -1;
@@ -1347,25 +1329,6 @@ class _CustomHashSet<E> extends _HashSet<E> {
     if (!_validKey(object)) return false;
     return super._remove(object);
   }
-
-  bool containsAll(Iterable<Object> elements) {
-    for (Object element in elements) {
-      if (!_validKey(element) || !this.contains(element)) return false;
-    }
-    return true;
-  }
-
-  void removeAll(Iterable<Object> elements) {
-    for (Object element in elements) {
-      if (_validKey(element)) {
-        super._remove(element);
-      }
-    }
-  }
-
-  void retainAll(Iterable<Object> elements) {
-    super._retainAll(elements, _validKey);
-  }
 }
 
 // TODO(kasperl): Share this code with HashMapKeyIterator<E>?
@@ -1431,7 +1394,7 @@ patch class LinkedHashSet<E> {
   patch factory LinkedHashSet.identity() = _LinkedIdentityHashSet<E>;
 }
 
-class _LinkedHashSet<E> extends _HashSetBase<E> implements LinkedHashSet<E> {
+class _LinkedHashSet<E> extends SetBase<E> implements LinkedHashSet<E> {
   int _length = 0;
 
   // The hash set contents are divided into three parts: one part for
@@ -1459,7 +1422,7 @@ class _LinkedHashSet<E> extends _HashSetBase<E> implements LinkedHashSet<E> {
 
   _LinkedHashSet();
 
-  Set<E> _newSet() => new _LinkedHashSet<E>();
+  Set<E> cloneEmpty() => new _LinkedHashSet<E>();
 
   void _unsupported(String operation) {
     throw 'LinkedHashSet: unsupported $operation';
@@ -1568,12 +1531,6 @@ class _LinkedHashSet<E> extends _HashSetBase<E> implements LinkedHashSet<E> {
     return true;
   }
 
-  void addAll(Iterable<E> objects) {
-    for (E object in objects) {
-      add(object);
-    }
-  }
-
   bool remove(Object object) {
     if (_isStringElement(object)) {
       return _removeHashTableEntry(_strings, object);
@@ -1597,16 +1554,6 @@ class _LinkedHashSet<E> extends _HashSetBase<E> implements LinkedHashSet<E> {
     return true;
   }
 
-  void removeAll(Iterable objectsToRemove) {
-    for (var each in objectsToRemove) {
-      remove(each);
-    }
-  }
-
-  void retainAll(Iterable<Object> elements) {
-    super._retainAll(elements, (o) => o is E);
-  }
-
   void removeWhere(bool test(E element)) {
     _filterWhere(test, true);
   }
@@ -1759,7 +1706,7 @@ class _LinkedHashSet<E> extends _HashSetBase<E> implements LinkedHashSet<E> {
 }
 
 class _LinkedIdentityHashSet<E> extends _LinkedHashSet<E> {
-  Set<E> _newSet() => new _LinkedIdentityHashSet<E>();
+  Set<E> cloneEmpty() => new _LinkedIdentityHashSet<E>();
 
   int _computeHashCode(var key) {
     // We force the hash codes to be unsigned 30-bit integers to avoid
@@ -1787,7 +1734,7 @@ class _LinkedCustomHashSet<E> extends _LinkedHashSet<E> {
                        bool validKey(potentialKey))
       : _validKey = (validKey != null) ? validKey : ((x) => x is E);
 
-  Set<E> _newSet() =>
+  Set<E> cloneEmpty() =>
       new _LinkedCustomHashSet<E>(_equality, _hasher, _validKey);
 
   int _findBucketIndex(var bucket, var element) {
@@ -1839,10 +1786,6 @@ class _LinkedCustomHashSet<E> extends _LinkedHashSet<E> {
       }
     }
   }
-
-  void retainAll(Iterable<Object> elements) {
-    super._retainAll(elements, _validKey);
-  }
 }
 
 class LinkedHashSetCell {