Properly handle errors thrown in [Chain.capture]'s [onError] handler.

pkg/stack_trace/test/chain_test.dart

 // Copyright (c) 2013, 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 chain_test;
 
 import 'dart:async';
 
 import 'package:path/path.dart' as p;
 import 'package:stack_trace/stack_trace.dart';
@@ skipping 89 matching lines @@
         } else {
           expect(error, equals('second error'));
           expect(chain.traces[1].frames,
               contains(frameMember(startsWith('inPeriodicTimer'))));
           completer.complete();
         }
       });
 
       return completer.future;
     });
+
+    test('and relays them to the parent zone', () {
+      var completer = new Completer();
+
+      runZoned(() {
+        Chain.capture(() {
+          inMicrotask(() => throw 'error');
+        }, onError: (error, chain) {
+          expect(error, equals('error'));
+          expect(chain.traces[1].frames,
+              contains(frameMember(startsWith('inMicrotask'))));
+          throw error;
+        });
+      }, onError: (error, chain) {
+        expect(error, equals('error'));
+        expect(chain, new isInstanceOf<Chain>());
+        expect(chain.traces[1].frames,
+            contains(frameMember(startsWith('inMicrotask'))));
+        completer.complete();
+      });
+
+      return completer.future;
+    });
   });
 
   test('capture() without onError passes exceptions to parent zone', () {
     var completer = new Completer();
 
     runZoned(() {
       Chain.capture(() => inMicrotask(() => throw 'error'));
     }, onError: (error, chain) {
       expect(error, equals('error'));
       expect(chain, new isInstanceOf<Chain>());
@@ skipping 567 matching lines @@
 ///
 /// [callback] is expected to throw the string `"error"`.
 Future<Chain> captureFuture(callback()) {
   var completer = new Completer<Chain>();
   Chain.capture(callback, onError: (error, chain) {
     expect(error, equals('error'));
     completer.complete(chain);
   });
   return completer.future;
 }