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

dart/lib/compiler/implementation/lib/core_patch.dart

Index: dart/lib/compiler/implementation/lib/core_patch.dart
diff --git a/dart/lib/compiler/implementation/lib/core_patch.dart b/dart/lib/compiler/implementation/lib/core_patch.dart
index bc881b3391220ec29540977276584feb97808576..70ac1c3ac87b32c5c11be9f9646cf0372033a8c4 100644
--- a/dart/lib/compiler/implementation/lib/core_patch.dart
+++ b/dart/lib/compiler/implementation/lib/core_patch.dart
@@ -65,3 +65,16 @@ patch class int {
 patch class double {
   patch static double parse(String string) => Primitives.parseDouble(string);
 }
+
+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 Primitives.objectToString(object);
+  }
+}