[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;
+
+  // The backing thread is cleared by clearSharedBackingThread().
+  void clearWorkerBackingThread() override {}
+
+  bool shouldAttachThreadDebugger() const override { return false; }
+
+  // This may block the main thread.
+  static void collectAllGarbage();
+
+  static void ensureSharedBackingThread();
+  static void createSharedBackingThreadForTest();
+
+  static void clearSharedBackingThread();
+
+ protected:
+  WorkerOrWorkletGlobalScope* createWorkerGlobalScope(
+      std::unique_ptr<WorkerThreadStartupData>) final;
+
+  bool isOwningBackingThread() const override { return false; }
+
+ private:
+  explicit AudioWorkletThread(PassRefPtr<WorkerLoaderProxy>,
+                              WorkerReportingProxy&);
+};
+
+}  // namespace blink
+
+#endif  // AudioWorkletThread_h