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

Index: runtime/bin/vmservice/observatory/lib/src/elements/observatory_element.dart
diff --git a/runtime/bin/vmservice/observatory/lib/src/elements/observatory_element.dart b/runtime/bin/vmservice/observatory/lib/src/elements/observatory_element.dart
index 4dccf987b54d039ec03ae8d79fb81c3e221dd8fc..1141def5ee66e662aae0a149a9601f220a167931 100644
--- a/runtime/bin/vmservice/observatory/lib/src/elements/observatory_element.dart
+++ b/runtime/bin/vmservice/observatory/lib/src/elements/observatory_element.dart
@@ -111,4 +111,28 @@ class ObservatoryElement extends PolymerElement {
   }
 
   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);
+  }
 }