[worklets] Add AudioWorkletGlobalScope and AudioWorkletThread

third_party/WebKit/Source/modules/webaudio/AudioWorkletThread.h

+// Copyright 2016 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 AudioWorkletThread_h
+#define AudioWorkletThread_h
+
+#include "core/workers/WorkerLoaderProxy.h"
+#include "core/workers/WorkerThread.h"
+#include "modules/ModulesExport.h"
+#include <memory>
+
+namespace blink {
+
+class WorkerReportingProxy;
+
+// AudioWorkletThread is a per-frame singleton object that represents the
+// backing thread for the processing of AudioWorkletNode/AudioWorkletProcessor.
+// It is supposed to run an instance of V8 isolate.
+
+class MODULES_EXPORT AudioWorkletThread final : public WorkerThread {
+public:
+    static std::unique_ptr<AudioWorkletThread> create(PassRefPtr<WorkerLoaderProxy>, WorkerReportingProxy&);
+    ~AudioWorkletThread() override;
+
+    WorkerBackingThread& workerBackingThread() override;
+    void clearWorkerBackingThread() override
+    {
+        // Do nothing.
+        // The backing thread is cleared by clearSharedBackingThread().
+    }
+
+    bool shouldAttachThreadDebugger() const override { return false; }
+
+    static void collectAllGarbage();

[nhiroki, 2016/09/30 11:28:57]

Can you add a comment that this may block the main thread?

[hongchan, 2016/10/11 23:42:38]

Done. 

+
+    static void ensureSharedBackingThread();
+    static void createSharedBackingThreadForTest();
+    static void clearSharedBackingThread();
+
+protected:
+    WorkerOrWorkletGlobalScope* createWorkerGlobalScope(std::unique_ptr<WorkerThreadStartupData>) final;
+
+    bool isOwningBackingThread() const override { return false; }
+
+private:
+    AudioWorkletThread(PassRefPtr<WorkerLoaderProxy>, WorkerReportingProxy&);
+};
+
+} // namespace blink
+
+#endif // AudioWorkletThread_h