Revert "Remove Sink and move CollectionSink to async."

sdk/lib/core/sink.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.async;
+part of dart.core;
+/**
+ * An interface for an object that can receive a sequence of values.
+ */
+abstract class Sink<T> {
+  /** Write a value to the sink. */
+  add(T value);
+  /** Tell the sink that no further values will be written. */
+  void close();
+}
+
+// ----------------------------------------------------------------------
+// Collections/Sink interoperability
+// ----------------------------------------------------------------------
 
 typedef void _CollectionSinkCallback<T>(Collection<T> collection);
-typedef void _CollectionSinkErrorCallback(AsyncError error);
 
 /** Sink that stores incoming data in a collection. */
-class CollectionSink<T> implements StreamSink<T> {
+class CollectionSink<T> implements Sink<T> {
   final Collection<T> collection;
-  final _CollectionSinkCallback<T> _callback;
-  final _CollectionSinkErrorCallback _errorCallback;
+  final _CollectionSinkCallback<T> callback;
   bool _isClosed = false;
 
   /**
    * Create a sink that stores incoming values in a collection.
    *
    * The [collection] is the collection to add the values to.
    *
    * If [callback] is provided, then it's called with the collection as arugment
    * when the sink's [close] method is called.
    */
-  CollectionSink(this.collection,
-                { void onClose(Collection<T> collection),
-                  void onError(AsyncError error) })
-      : this._callback = onClose,
-        this._errorCallback = onError;
+  CollectionSink(this.collection, [void callback(Collection<T> collection)])
+      : this.callback = callback;
 
   add(T value) {
     if (_isClosed) throw new StateError("Adding to closed sink");
     collection.add(value);
   }
 
-  void signalError(AsyncError error) {
-    if (_isClosed) throw new StateError("Singalling error on closed sink");
-    if (_errorCallback != null) _errorCallback(error);
-  }
-
   void close() {
     if (_isClosed) throw new StateError("Closing closed sink");
     _isClosed = true;
-    if (_callback != null) _callback(collection);
+    if (callback != null) callback(collection);
   }
 }