Add Isolate.current getter, returning the current isolate as an Isolate object.

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 Capability {
   /* patch */ factory Capability() = _CapabilityImpl;
 }
 
 class _CapabilityImpl implements Capability {
   factory _CapabilityImpl() native "CapabilityImpl_factory";
+
+  String toString() => "Capability#";
 }
 
 patch class RawReceivePort {
   /**
    * Opens a long-lived port for receiving messages.
    *
    * A [RawReceivePort] is low level and does not work with [Zone]s. It
    * can not be paused. The data-handler must be set before the first
    * event is received.
    */
@@ skipping 208 matching lines @@
     } else {
       entryPoint();
     }
   } else {
     entryPoint(message);
   }
   _runPendingImmediateCallback();
 }
 
 patch class Isolate {
+  static final _currentIsolate = _getCurrentIsolate();
+
+  /* patch */ static Isolate get current => _currentIsolate;
+
   /* patch */ static Future<Isolate> spawn(
       void entryPoint(message), var message, { bool paused: false }) {
     // `paused` isn't handled yet.
     RawReceivePort readyPort;
     try {
       // The VM will invoke [_startIsolate] with entryPoint as argument.
       readyPort = new RawReceivePort();
       _spawnFunction(readyPort.sendPort, entryPoint, message);
       Completer completer = new Completer<Isolate>.sync();
       readyPort.handler = (readyMessage) {
@@ skipping 103 matching lines @@
     throw new UnsupportedError("ping");
   }
 
   /* patch */ void addErrorListener(SendPort port) {
     throw new UnsupportedError("addErrorListener");
   }
 
   /* patch */ void removeErrorListener(SendPort port) {
     throw new UnsupportedError("removeErrorListener");
   }
+
+  static Isolate _getCurrentIsolate() {
+    List portAndCapabilities = _getPortAndCapabilitiesOfCurrentIsolate();
+    return new Isolate(portAndCapabilities[0],
+                       pauseCapability: portAndCapabilities[1],
+                       terminateCapability: portAndCapabilities[2]);
+  }
+
+  static List _getPortAndCapabilitiesOfCurrentIsolate()
+      native "Isolate_getPortAndCapabilitiesOfCurrentIsolate";
 }