Get new tests working on dart2js.

lib/src/invoker.dart

 // Copyright (c) 2015, 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 unittest.invoker;
 
 import 'dart:async';
 
 import 'package:stack_trace/stack_trace.dart';
 
@@ skipping 51 matching lines @@
 
   /// The completer to complete once the test body finishes.
   ///
   /// This is distinct from [_controller.completer] because a tear-down may need
   /// to run before the test is truly finished.
   final _completer = new Completer();
 
   /// The current invoker, or `null` if none is defined.
   ///
   /// An invoker is only set within the zone scope of a running test.
-  static Invoker get current => Zone.current[#unittest._invoker];
+  static Invoker get current {
+    // TODO(nweiz): Use a private symbol when dart2js supports it (issue 17526).
+    return Zone.current[#unittest.invoker];
+  }
 
   Invoker._(Suite suite, LocalTest test) {
     _controller = new LiveTestController(suite, test, _onRun);
   }
 
   /// Tells the invoker that there's a callback running that it should wait for
   /// before considering the test successful.
   ///
   /// Each call to [addOutstandingCallback] should be followed by a call to
   /// [removeOutstandingCallback] once the callbak is no longer running. Note
@@ skipping 81 matching lines @@
         // avoid that.
         _completer.future.then((_) {
           if (_test._tearDown == null) return null;
           return new Future.sync(_test._tearDown);
         }).catchError(Zone.current.handleUncaughtError).then((_) {
           timer.cancel();
           _controller.setState(
               new State(Status.complete, liveTest.state.result));
           _controller.completer.complete();
         });
-      }, zoneValues: {#unittest._invoker: this}, onError: handleError);
+      }, zoneValues: {#unittest.invoker: this}, onError: handleError);
     });
   }
 }