Remove StreamSink(replaced by EventSink) and make IOSink extend EventSink.

tests/isolate/global_error_handler_stream_test.dart

 // Copyright (c) 2013, 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.
 
 library test;
 
 import 'dart:async';
 import 'dart:isolate';
 
 var firstFunction;
 var finishFunction;
 
 void runFunctions() {
   try {
     firstFunction();
   } catch (e) {
     new Timer(Duration.ZERO, finishFunction);
     throw;
   }
 }
 
-void startTest(StreamSink finishSink) {
+void startTest(EventSink finishSink) {
   firstFunction = () { throw new RuntimeError("ignore exception"); };
   finishFunction = () { finishSink.add("done"); finishSink.close(); };
   new Timer(Duration.ZERO, runFunctions);
 }
 
 runTest() {
   stream.single.then(startTest);
 }
 
 bool globalErrorHandler(IsolateUnhandledException e) {
   return e.source is RuntimeError && e.source.message == "ignore exception";
 }
 
 main() {
   var box = new MessageBox();
   var timer;
-  StreamSink otherIsolate = streamSpawnFunction(runTest, globalErrorHandler);
+  EventSink otherIsolate = streamSpawnFunction(runTest, globalErrorHandler);
   otherIsolate.add(box.sink);
   otherIsolate.close();
   box.stream.single.then((msg) {
     box.stream.close();
     timer.cancel();
   });
   timer = new Timer(const Duration(seconds: 2), () { throw "failed"; });
 }