Don't invoke user-defined code in NoSuchMethodError.toString.

dart/runtime/lib/errors_patch.dart

Index: dart/runtime/lib/errors_patch.dart
diff --git a/dart/runtime/lib/errors_patch.dart b/dart/runtime/lib/errors_patch.dart
new file mode 100644
index 0000000000000000000000000000000000000000..c118932ae6e3c15d2611c5cd0c2bc7ebca30e4ab
--- /dev/null
+++ b/dart/runtime/lib/errors_patch.dart
@@ -0,0 +1,16 @@
+// Copyright (c) 2012, 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.
+
+patch class NoSuchMethodError {
+  /* patch */ static String safeToString(Object object) {
+    if (object is int || object is double || object is bool || null == object) {
+      return object.toString();
+    }
+    if (object is String) {
+      String escaped = object.replaceAll('"', '\\"');
+      return '"$escaped"';
+    }
+    return Object._toString(object);
+  }
+}