Don't double-escape in strings in the VM Service, and don't use \u0000 to determine the string lengt

runtime/bin/vmservice/observatory/lib/src/elements/observatory_element.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 observatory_element;
 
 import 'dart:async';
 import 'dart:html';
 import 'package:observatory/app.dart';
 import 'package:polymer/polymer.dart';
@@ skipping 93 matching lines @@
 
   String formatSize(int bytes) => Utils.formatSize(bytes);
 
   String fileAndLine(Map frame) {
     var file = frame['script'].name;
     var shortFile = file.substring(file.lastIndexOf('/') + 1);
     return "${shortFile}:${frame['line']}";
   }
 
   int parseInt(String value) => int.parse(value);
+
+  String asStringLiteral(String value, [bool wasTruncated=false]) {
+    var result = new List();
+    result.add("'".codeUnitAt(0));
+    for (int codeUnit in value.codeUnits) {
+      if (codeUnit == '\n'.codeUnitAt(0)) result.addAll('\\n'.codeUnits);
+      else if (codeUnit == '\r'.codeUnitAt(0)) result.addAll('\\r'.codeUnits);
+      else if (codeUnit == '\f'.codeUnitAt(0)) result.addAll('\\f'.codeUnits);
+      else if (codeUnit == '\b'.codeUnitAt(0)) result.addAll('\\b'.codeUnits);
+      else if (codeUnit == '\t'.codeUnitAt(0)) result.addAll('\\t'.codeUnits);
+      else if (codeUnit == '\v'.codeUnitAt(0)) result.addAll('\\v'.codeUnits);
+      else if (codeUnit == '\$'.codeUnitAt(0)) result.addAll('\\\$'.codeUnits);
+      else if (codeUnit == '\\'.codeUnitAt(0)) result.addAll('\\\\'.codeUnits);
+      else if (codeUnit == "'".codeUnitAt(0)) result.addAll("'".codeUnits);
+      else if (codeUnit < 32) result.addAll("\\u$codeUnit".codeUnits);
+      else result.add(codeUnit);
+    }
+    if (wasTruncated) {
+      result.addAll("...".codeUnits);
+    } else {
+      result.add("'".codeUnitAt(0));
+    }
+    return new String.fromCharCodes(result);
+  }
 }