Worklet: Separate Worklet into MainThreadWorklet and ThreadedWorklet

third_party/WebKit/Source/core/workers/MainThreadWorklet.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 MainThreadWorklet_h
+#define MainThreadWorklet_h
+
+#include "core/workers/Worklet.h"
+
+#include "bindings/core/v8/ScriptPromiseResolver.h"
+#include "core/CoreExport.h"
+#include "core/loader/WorkletScriptLoader.h"
+#include "platform/heap/Handle.h"
+
+namespace blink {
+
+class LocalFrame;
+
+// TODO(nhiroki): This is a temporary class to support module loading for main
+// thread worklets. This and ThreadedWorklet will be merged into the base
+// Worklet class once threaded worklets are ready to use module loading.

[falken, 2017/04/17 05:35:54]

In addition to the TODO, can you have a basic comment about what a main thread
worklet is? "A MainThreadWorklet is a worklet that runs only on the main
thread."

[nhiroki, 2017/04/17 11:35:04]

Done.

+class CORE_EXPORT MainThreadWorklet : public Worklet,
+                                      public WorkletScriptLoader::Client {
+  USING_GARBAGE_COLLECTED_MIXIN(MainThreadWorklet);
+  WTF_MAKE_NONCOPYABLE(MainThreadWorklet);
+
+ public:
+  virtual ~MainThreadWorklet() = default;
+
+  // Worklet
+  ScriptPromise import(ScriptState*, const String& url) final;
+
+  // WorkletScriptLoader::Client
+  void NotifyWorkletScriptLoadingFinished(WorkletScriptLoader*,
+                                          const ScriptSourceCode&) final;
+
+  // ContextLifecycleObserver
+  void ContextDestroyed(ExecutionContext*) final;
+
+  DECLARE_VIRTUAL_TRACE();
+
+ protected:
+  explicit MainThreadWorklet(LocalFrame*);
+
+ private:
+  HeapHashMap<Member<WorkletScriptLoader>, Member<ScriptPromiseResolver>>
+      loader_and_resolvers_;

[falken, 2017/04/17 05:35:54]

nit: this name doesn't really sound like a map. |loader_to_resolver_map_|?

[nhiroki, 2017/04/17 11:35:04]

Done.

+};
+
+}  // namespace blink
+
+#endif  // MainThreadWorklet_h