Update and fix isolate documentation.

runtime/lib/isolate_patch.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.
 
+import "dart:collection" show HashMap;
+
 patch class ReceivePort {
   /* patch */ factory ReceivePort() = _ReceivePortImpl;
 
   /* patch */ factory ReceivePort.fromRawReceivePort(RawReceivePort rawPort) =
       _ReceivePortImpl.fromRawReceivePort;
 }
 
 patch class RawReceivePort {
   /**
    * Opens a long-lived port for receiving messages.
@@ skipping 226 matching lines @@
   }
 
   static final RawReceivePort _self = _mainPort;
   static RawReceivePort get _mainPort native "Isolate_mainPort";
 
   static SendPort _spawnFunction(Function topLevelFunction)
       native "Isolate_spawnFunction";
 
   static SendPort _spawnUri(String uri) native "Isolate_spawnUri";
 }