Fold empty async frames when generating a terse stack trace.

test/trace_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 trace_test;
 
 import 'package:path/path.dart' as path;
 import 'package:stack_trace/stack_trace.dart';
 import 'package:unittest/unittest.dart';
 
@@ skipping 265 matching lines @@
 ''');
 
     expect(trace.terse.toString(), equals('''
 foo.dart 42:21  notCore
 dart:core       bottom
 bar.dart 10:20  alsoNotCore
 dart:async      bottom
 '''));
   });
 
+  test('.terse folds empty async frames', () {
+    var trace = new Trace.parse('''
+#0 notCore (foo.dart:42:21)
+#1 top (dart:async/future.dart:0:2)
+#2 empty.<<anonymous closure>_async_body> (bar.dart)
+#3 bottom (dart:async-patch/future.dart:9:11)
+''');
+
+    expect(trace.terse.toString(), equals('''
+foo.dart 42:21  notCore
+dart:async      bottom
+'''));
+  });
+
   test('.foldFrames folds frames together bottom-up', () {
     var trace = new Trace.parse('''
 #0 notFoo (foo.dart:42:21)
 #1 fooTop (bar.dart:0:2)
 #2 fooBottom (foo.dart:1:100)
 #3 alsoNotFoo (bar.dart:10:20)
 #4 fooTop (dart:io/socket.dart:5:10)
 #5 fooBottom (dart:async-patch/future.dart:9:11)
 ''');
 
     var folded = trace.foldFrames((frame) => frame.member.startsWith('foo'));
     expect(folded.toString(), equals('''
 foo.dart 42:21                     notFoo
 foo.dart 1:100                     fooBottom
 bar.dart 10:20                     alsoNotFoo
 dart:async-patch/future.dart 9:11  fooBottom
 '''));
   });
 }