Fix Error.prototype.toString to throw TypeError.

src/messages.js

Index: src/messages.js
diff --git a/src/messages.js b/src/messages.js
index e641133dda585fe2071c176664ba7bc77202200c..5c722d60666a739b02eeb0ae96b7344c1e1d987b 100644
--- a/src/messages.js
+++ b/src/messages.js
@@ -210,7 +210,7 @@ function FormatMessage(message) {
       "no_input_to_regexp",           ["No input to ", "%0"],
       "invalid_json",                 ["String '", "%0", "' is not valid JSON"],
       "circular_structure",           ["Converting circular structure to JSON"],
-      "obj_ctor_property_non_object", ["Object.", "%0", " called on non-object"],
+      "called_on_non_object",         ["%0", " called on non-object"],
       "called_on_null_or_undefined",  ["%0", " called on null or undefined"],
       "array_indexof_not_defined",    ["Array.getIndexOf: Argument undefined"],
       "object_not_extensible",        ["Can't add property ", "%0", ", object is not extensible"],
@@ -1190,9 +1190,8 @@ function ErrorToStringDetectCycle(error) {
 }
 
 function ErrorToString() {
-  if (IS_NULL_OR_UNDEFINED(this) && !IS_UNDETECTABLE(this)) {
-    throw MakeTypeError("called_on_null_or_undefined",
-                        ["Error.prototype.toString"]);
+  if (!IS_SPEC_OBJECT(this)) {
+    throw MakeTypeError("called_on_non_object", ["Error.prototype.toString"]);
   }
 
   try {