Make the stack_trace package print relative URLs for browser paths.

pkg/stack_trace/test/frame_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 frame_test;
 
 import 'package:path/path.dart' as path;
 import 'package:stack_trace/stack_trace.dart';
 import 'package:unittest/unittest.dart';
 
@@ skipping 477 matching lines @@
     test('converts "<anonymous closure>" to "<fn>"', () {
       expect(new Frame.parseVM('#0 Foo.<anonymous closure> '
               '(dart:core/uri.dart:5:10)').toString(),
           equals('dart:core/uri.dart 5:10 in Foo.<fn>'));
     });
 
     test('prints a frame without a column correctly', () {
       expect(new Frame.parseVM('#0 Foo (dart:core/uri.dart:5)').toString(),
           equals('dart:core/uri.dart 5 in Foo'));
     });
+
+    test('prints relative paths as relative', () {
+      var relative = path.normalize('relative/path/to/foo.dart');
+      expect(new Frame.parseFriendly('$relative 5:10  Foo').toString(),
+          equals('$relative 5:10 in Foo'));
+    });
   });
 }