[ES6 modules] Return previous error when an instantiation is reattempt.

third_party/WebKit/Source/core/testing/DummyModulator.cpp

 // Copyright 2017 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "core/testing/DummyModulator.h"
 
 #include "bindings/core/v8/ScriptValue.h"
 
 namespace blink {
 
@@ skipping 59 matching lines @@
                                            AccessControlStatus) {
   NOTREACHED();
   return ScriptModule();
 }
 
 ScriptValue DummyModulator::InstantiateModule(ScriptModule) {
   NOTREACHED();
   return ScriptValue();
 }
 
+ScriptValue DummyModulator::GetInstantiationError(const ModuleScript*) {
+  NOTREACHED();
+  return ScriptValue();
+}
+
 Vector<String> DummyModulator::ModuleRequestsFromScriptModule(ScriptModule) {
   NOTREACHED();
   return Vector<String>();
 }
 
 void DummyModulator::ExecuteModule(const ModuleScript*) {
   NOTREACHED();
 }
 
 }  // namespace blink