Another fix for leaking error objects. User code can overwrite

test/cctest/test-api.cc

Index: test/cctest/test-api.cc
diff --git a/test/cctest/test-api.cc b/test/cctest/test-api.cc
index de00fbba4635a2543775d74ba5e3efa5d8367a43..90f499674299768599b7986e8674a487fe54c10f 100644
--- a/test/cctest/test-api.cc
+++ b/test/cctest/test-api.cc
@@ -2383,6 +2383,10 @@ TEST(APIThrowMessageOverwrittenToString) {
   CompileRun("asdf;");
   CompileRun("ReferenceError.prototype.constructor = void 0;");
   CompileRun("asdf;");
+  CompileRun("ReferenceError.prototype.__proto__ = new Object();");
+  CompileRun("asdf;");
+  CompileRun("ReferenceError.prototype = new Object();");
+  CompileRun("asdf;");
   v8::Handle<Value> string = CompileRun("try { asdf; } catch(e) { e + ''; }");
   CHECK(string->Equals(v8_str("Whoops")));
   v8::V8::RemoveMessageListeners(check_message);