Use the stack_trace library in scheduled_test.

pkg/stack_trace/lib/src/frame.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;
 
 import 'dart:uri';
 
 import 'package:pathos/path.dart' as path;
 
@@ skipping 28 matching lines @@
   /// comes from.
   ///
   /// This will usually be the string form of [uri], but a relative path will be
   /// used if possible.
   String get library {
     // TODO(nweiz): handle relative URIs here as well once pathos supports that.
     if (uri.scheme != 'file') return uri.toString();
     return path.relative(fileUriToPath(uri));
   }
 
+  /// Returns the name of the package this stack frame comes from, or `null` if
+  /// this stack frame doesn't come from a `package:` URL.
+  String get package {
+    if (uri.scheme != 'package') return null;
+    return uri.path.split('/').first;
+  }
+
   /// A human-friendly description of the code location.
   ///
   /// For Dart core libraries, this will omit the line and column information,
   /// since those are useless for baked-in libraries.
   String get location {
     if (isCore) return library;
     return '$library $line:$column';
   }
 
   /// Returns a single frame of the current stack.
@@ skipping 21 matching lines @@
 
     var uri = new Uri.fromString(match[2]);
     var member = match[1].replaceAll("<anonymous closure>", "<fn>");
     return new Frame(uri, int.parse(match[3]), int.parse(match[4]), member);
   }
 
   Frame(this.uri, this.line, this.column, this.member);
 
   String toString() => '$location in $member';
 }