isolates refactor: this change introduces 'dart:isolate' as a library. This is a

tests/standalone/src/SocketCloseTest.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.
 //
 // VMOptions=
 // VMOptions=--short_socket_read
 // VMOptions=--short_socket_write
 // VMOptions=--short_socket_read --short_socket_write
 //
 // Test socket close events.
 
 #import("dart:io");
+#import("dart:isolate");
 
 final SERVERSHUTDOWN = -1;
 final ITERATIONS = 10;
 
 
 class SocketClose {
 
   SocketClose.start(this._mode, this._donePort)
       : _receivePort = new ReceivePort(),
         _sendPort = null,
@@ skipping 356 matching lines @@
   var tests = 7;
   var port = new ReceivePort();
   var completed = 0;
   port.receive((message, ignore) {
     if (++completed == tests) port.close();
   });
   for (var i = 0; i < tests; i++) {
     new SocketClose.start(i, port.toSendPort());
   }
 }