[ES6 modules] Introduce ModuleScript model object

third_party/WebKit/Source/core/dom/ModuleScript.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/dom/ModuleScript.h"
+
+namespace blink {
+
+void ModuleScript::updateStateAfterInstantiation(ScriptValue maybeError) {

[domenic, 2017/01/19 05:23:59]

This method seems redundant. It is only used once in
https://codereview.chromium.org/2555653002/ and there it is always called with
ScriptValue(), so I think that usage can be replaced with
propagateUpstreamSuccess().

+  DCHECK_EQ(m_instantiationState, InstantiationState::Uninstantiated);
+  m_instantiationState = maybeError.isEmpty() ? InstantiationState::Instantiated
+                                              : InstantiationState::Errored;
+  m_instantiationError = maybeError;
+}
+
+void ModuleScript::propagateUpstreamError(ScriptValue error) {

[domenic, 2017/01/19 05:23:59]

Ideally these would have unit tests. Not sure what the unit testing culture is
like in Blink.

+  DCHECK_EQ(m_instantiationState, InstantiationState::Uninstantiated);
+  m_instantiationState = InstantiationState::Errored;
+  m_instantiationError = error;
+}
+
+void ModuleScript::propagateUpstreamSuccess() {
+  DCHECK_EQ(m_instantiationState, InstantiationState::Uninstantiated);
+  m_instantiationState = InstantiationState::Instantiated;
+}
+
+}  // namespace blink