[ES6 modules] Introduce ModuleTreeLinker

third_party/WebKit/Source/core/loader/modulescript/ModuleTreeLinkerRegistry.h

+// 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.
+
+#ifndef ModuleTreeLinkerRegistry_h
+#define ModuleTreeLinkerRegistry_h
+
+#include "core/CoreExport.h"
+#include "core/dom/AncestorList.h"
+#include "platform/heap/Handle.h"
+
+namespace blink {
+
+class Modulator;
+class ModuleScriptFetchRequest;
+class ModuleTreeClient;
+class ModuleTreeLinker;
+enum class ModuleGraphLevel;
+
+// ModuleTreeLinkerRegistry keeps active ModuleTreeLinkers alive.
+class CORE_EXPORT ModuleTreeLinkerRegistry
+    : public GarbageCollected<ModuleTreeLinkerRegistry> {
+ public:
+  static ModuleTreeLinkerRegistry* Create() {
+    return new ModuleTreeLinkerRegistry;
+  }
+  DECLARE_TRACE();
+
+  ModuleTreeLinker* Fetch(const ModuleScriptFetchRequest&,
+                          const AncestorList&,
+                          ModuleGraphLevel,
+                          Modulator*,
+                          ModuleTreeClient*);
+
+ private:
+  ModuleTreeLinkerRegistry() = default;
+
+  friend class ModuleTreeLinker;
+  void ReleaseFinishedFetcher(ModuleTreeLinker*);
+
+  HeapHashSet<Member<ModuleTreeLinker>> active_tree_linkers_;
+};
+
+}  // namespace blink
+
+#endif