Add a couple functions to package:stack_trace.

pkg/stack_trace/lib/src/vm_trace.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 vm_trace;
+
+import 'frame.dart';
+import 'utils.dart';
+
+/// An implementation of [StackTrace] that emulates the behavior of the VM's
+/// implementation.
+///
+/// In particular, when [toString] is called, this returns a string in the VM's
+/// stack trace format.
+class VMTrace implements StackTrace {
+  /// The stack frames that comprise this stack trace.
+  final List<Frame> frames;
+
+  VMTrace(this.frames);
+
+  String toString() {
+    var i = 1;
+    return frames.map((frame) {
+      var number = padRight("#${i++}", 8);
+      var member = frame.member.replaceAll("<fn>", "<anonymous closure>");
+      var line = frame.line == null ? 0 : frame.line;
+      var column = frame.column == null ? 0 : frame.column;
+      return "$number$member (${frame.uri}:$line:$column)\n";
+    }).join();
+  }
+}