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

sdk/lib/_internal/compiler/js_lib/isolate_helper.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.
 
 library _isolate_helper;
 
 import 'shared/embedded_names.dart' show
     CURRENT_SCRIPT,
     GLOBAL_FUNCTIONS;
 
@@ skipping 997 matching lines @@
           "Currently spawnUri is not supported without web workers.");
     }
     message = _serializeMessage(message);
     args = _serializeMessage(args);  // Or just args.toList() ?
     _globalState.topEventLoop.enqueue(new _IsolateContext(), () {
       final func = _getJSFunctionFromName(functionName);
       _startIsolate(func, args, message, isSpawnUri, startPaused, replyPort);
     }, 'nonworker start');
   }
 
+  static Isolate get currentIsolate {
+    _IsolateContext context = JS_CURRENT_ISOLATE_CONTEXT();
+    return new Isolate(context.controlPort.sendPort,
+                       pauseCapability: context.pauseCapability,
+                       terminateCapability: context.terminateCapability);
+  }
+
   static void _startIsolate(Function topLevel,
                             List<String> args, message,
                             bool isSpawnUri,
                             bool startPaused,
                             SendPort replyTo) {
     _IsolateContext context = JS_CURRENT_ISOLATE_CONTEXT();
     Primitives.initializeStatics(context.id);
     // The isolate's port does not keep the isolate open.
     replyTo.send([_SPAWNED_SIGNAL,
                   context.controlPort.sendPort,
@@ skipping 817 matching lines @@
   }
 
   bool operator==(Object other) {
     if (identical(other, this)) return true;
     if (other is CapabilityImpl) {
       return identical(_id, other._id);
     }
     return false;
   }
 }