[ES6 modules] Introduce ModuleTreeLinker

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

Index: third_party/WebKit/Source/core/loader/modulescript/ModuleTreeLinker.h
diff --git a/third_party/WebKit/Source/core/loader/modulescript/ModuleTreeLinker.h b/third_party/WebKit/Source/core/loader/modulescript/ModuleTreeLinker.h
new file mode 100644
index 0000000000000000000000000000000000000000..9446d409dca0928d6c4eb36c96c63752a5a084e4
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+++ b/third_party/WebKit/Source/core/loader/modulescript/ModuleTreeLinker.h
@@ -0,0 +1,89 @@
+// 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 ModuleTreeLinker_h
+#define ModuleTreeLinker_h
+
+#include "core/CoreExport.h"
+#include "core/dom/AncestorList.h"
+#include "core/dom/Modulator.h"
+
+namespace blink {
+
+class ModuleScriptFetchRequest;
+enum class ModuleGraphLevel;
+class ModuleTreeLinkerRegistry;
+
+// A ModuleTreeLinker is responsible for running and keeping intermediate states
+// for "internal module script graph fetching procedure" for a module graph tree
+// node.
+// https://html.spec.whatwg.org/multipage/webappapis.html#internal-module-script-graph-fetching-procedure
+class CORE_EXPORT ModuleTreeLinker final
+    : public GarbageCollectedFinalized<ModuleTreeLinker>,
+      public SingleModuleClient {
+  USING_GARBAGE_COLLECTED_MIXIN(ModuleTreeLinker);
+
+ public:
+  static ModuleTreeLinker* Fetch(const ModuleScriptFetchRequest&,
+                                 const AncestorList&,
+                                 ModuleGraphLevel,
+                                 Modulator*,
+                                 ModuleTreeLinkerRegistry*,
+                                 ModuleTreeClient*);
+  virtual ~ModuleTreeLinker() = default;
+  DECLARE_TRACE();
+
+  bool IsFetching() const {
+    return State::kFetchingSelf <= state_ && state_ < State::kFinished;
+  }
+  bool HasFinished() const { return state_ == State::kFinished; }
+
+ private:
+  ModuleTreeLinker(const AncestorList& ancestor_list_with_url,
+                   Modulator*,
+                   ModuleTreeLinkerRegistry*,
+                   ModuleTreeClient*);
+
+  enum class State {
+    kInitial,
+    // Running fetch of the module script corresponding to the target node.
+    kFetchingSelf,
+    // Running fetch of descendants of the target node.
+    kFetchingDependencies,
+    // Instantiating m_moduleScript and the node descendants.
+    kInstantiating,
+    kFinished,
+  };
+#if DCHECK_IS_ON()
+  static const char* StateToString(State);
+#endif
+  void AdvanceState(State);
+
+  void FetchSelf(const ModuleScriptFetchRequest&, ModuleGraphLevel);
+  // Implements SingleModuleClient
+  void NotifyModuleLoadFinished(ModuleScript*) override;
+
+  void FetchDescendants();
+  enum class DescendantLoad { kFailed, kSuccess };
+  void NotifyOneDescendantFinished(DescendantLoad was_success);
+
+  void Instantiate();
+  HeapHashSet<Member<ModuleScript>> UninstantiatedInclusiveDescendants();
+
+  class DependencyModuleClient;
+  friend class DependencyModuleClient;
+
+  Member<Modulator> modulator_;
+  Member<ModuleTreeLinkerRegistry> registry_;
+  Member<ModuleTreeClient> client_;
+  HashSet<KURL> ancestor_list_with_url_;
+  State state_ = State::kInitial;
+  Member<ModuleScript> module_script_;
+  size_t num_incomplete_descendants_ = 0;
+  HeapHashSet<Member<DependencyModuleClient>> dependency_clients_;
+};
+
+}  // namespace blink
+
+#endif