anchor.diff:      if (msg.messageType == _Message.LOG) {
         logMessage(e.data);
       } else if (msg.messageType == _Message.STACK) {
  -      _stack = new Trace(json.parse(msg.body).map((frame) {
  +      _stack = new Trace(JSON.decode(msg.body).map((frame) {
           return new Frame(
               Uri.parse(frame['uri']),
               frame['line'],
  
positive.code: 
  import 'dart:html';
  import 'dart:async';
  import 'dart:json' as json;
  
  import 'package:stack_trace/stack_trace.dart';
  
  
negative.code:     DateTime end = new DateTime.now();
      int elapsed = end.difference(_testStarts[testCase.id]).inMilliseconds;
      if (testCase.stackTrace != null) {
        var message = JSON.encode(testCase.stackTrace.frames.map((frame) {
          return <String, dynamic>{
            "uri": frame.uri.toString(),
            "line": frame.line,
  