Issue #1603 - Part 2: Split some classes out of ScriptLoader.cpp

This splits ScriptLoader up the same way Mozilla did with the exception of
ScriptRequest due to the fact that ScriptLoader and ScriptRequest are
interdependent and would create a circular dependency if split apart when not
using unified building.

dom/script/ModuleScript.h

@@ -0,0 +1,67 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#ifndef mozilla_dom_ModuleScript_h
+#define mozilla_dom_ModuleScript_h
+
+#include "nsCOMPtr.h"
+#include "nsCycleCollectionParticipant.h"
+#include "jsapi.h"
+
+class nsIURI;
+
+namespace mozilla {
+namespace dom {
+
+class ScriptLoader;
+
+class ModuleScript final : public nsISupports
+{
+  enum InstantiationState {
+    Uninstantiated,
+    Instantiated,
+    Errored
+  };
+
+  RefPtr<ScriptLoader> mLoader;
+  nsCOMPtr<nsIURI> mBaseURL;
+  JS::Heap<JSObject*> mModuleRecord;
+  JS::Heap<JS::Value> mException;
+  InstantiationState mInstantiationState;
+
+  ~ModuleScript();
+
+public:
+  NS_DECL_CYCLE_COLLECTING_ISUPPORTS
+  NS_DECL_CYCLE_COLLECTION_SCRIPT_HOLDER_CLASS(ModuleScript)
+
+  ModuleScript(ScriptLoader* aLoader,
+               nsIURI* aBaseURL,
+               JS::Handle<JSObject*> aModuleRecord);
+
+  ScriptLoader* Loader() const { return mLoader; }
+  JSObject* ModuleRecord() const { return mModuleRecord; }
+  JS::Value Exception() const { return mException; }
+  nsIURI* BaseURL() const { return mBaseURL; }
+
+  void SetInstantiationResult(JS::Handle<JS::Value> aMaybeException);
+  bool IsUninstantiated() const {
+    return mInstantiationState == Uninstantiated;
+  }
+  bool IsInstantiated() const {
+    return mInstantiationState == Instantiated;
+  }
+  bool InstantiationFailed() const {
+    return mInstantiationState == Errored;
+  }
+
+  void UnlinkModuleRecord();
+};
+
+} // dom namespace
+} // mozilla namespace
+
+#endif // mozilla_dom_ModuleScript_h