Use the Zone API for registerException.

lib/src/backend/invoker.dart

Index: lib/src/backend/invoker.dart
diff --git a/lib/src/backend/invoker.dart b/lib/src/backend/invoker.dart
index 221c52a06a3667638c1ec85ea2efda388906d061..564dddad30a2951e786f9195461a38f7dfae0b5a 100644
--- a/lib/src/backend/invoker.dart
+++ b/lib/src/backend/invoker.dart
@@ -144,10 +144,7 @@ class Invoker {
   }
 
   /// Notifies the invoker of an asynchronous error.
-  ///
-  /// Note that calling this explicitly is rarely necessary, since any
-  /// otherwise-uncaught errors will be forwarded to the invoker anyway.
-  void handleError(error, [StackTrace stackTrace]) {
+  void _handleError(error, [StackTrace stackTrace]) {
     if (stackTrace == null) stackTrace = new Chain.current();
 
     var afterSuccess = liveTest.isComplete &&
@@ -165,7 +162,7 @@ class Invoker {
     // If a test was marked as success but then had an error, that indicates
     // that it was poorly-written and could be flaky.
     if (!afterSuccess) return;
-    handleError(
+    _handleError(
         "This test failed after it had already completed. Make sure to use "
             "[expectAsync]\n"
         "or the [completes] matcher when testing async code.",
@@ -187,7 +184,7 @@ class Invoker {
         var timeout = metadata.timeout.apply(new Duration(seconds: 30));
         var timer = new Timer(timeout, () {
           if (liveTest.isComplete) return;
-          handleError(
+          _handleError(
               new TimeoutException(
                   "Test timed out after ${niceDuration(timeout)}.", timeout));
         });
@@ -207,7 +204,7 @@ class Invoker {
           // Reset the outstanding callback counter to wait for callbacks from
           // the test's `tearDown` to complete.
           return waitForOutstandingCallbacks(() =>
-              runZoned(_test._tearDown, onError: handleError));
+              runZoned(_test._tearDown, onError: _handleError));
         }).then((_) {
           timer.cancel();
           _controller.setState(
@@ -225,7 +222,7 @@ class Invoker {
       },
           zoneSpecification: new ZoneSpecification(
               print: (self, parent, zone, line) => _controller.print(line)),
-          onError: handleError);
+          onError: _handleError);
     });
   }
 }