Make padding consistent across all stack traces for Chain.toString().

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 461 matching lines @@
         equals(new Trace.from(trace).toString()));
   });
 
   test('Chain.parse() parses a real Chain', () {
     return captureFuture(() => inMicrotask(() => throw 'error')).then((chain) {
       expect(new Chain.parse(chain.toString()).toString(),
           equals(chain.toString()));
     });
   });
 
+  test("toString() ensures that all traces are aligned", () {
+    var chain = new Chain([
+      new Trace.parse('short 10:11  Foo.bar\n'),
+      new Trace.parse('loooooooooooong 10:11  Zop.zoop')
+    ]);
+
+    expect(chain.toString(), equals(
+        'short 10:11            Foo.bar\n'
+        '===== asynchronous gap ===========================\n'
+        'loooooooooooong 10:11  Zop.zoop\n'));
+  });
+
   var userSlashCode = p.join('user', 'code.dart');
   group('Chain.terse', () {
     test('makes each trace terse', () {
       var chain = new Chain([
         new Trace.parse(
             'dart:core 10:11       Foo.bar\n'
             'dart:core 10:11       Bar.baz\n'
             'user/code.dart 10:11  Bang.qux\n'
             'dart:core 10:11       Zip.zap\n'
             'dart:core 10:11       Zop.zoop'),
@@ skipping 295 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;
 }