Introduce WorkerBackingThread

third_party/WebKit/Source/core/workers/WorkerBackingThread.h

Index: third_party/WebKit/Source/core/workers/WorkerBackingThread.h
diff --git a/third_party/WebKit/Source/core/workers/WorkerBackingThread.h b/third_party/WebKit/Source/core/workers/WorkerBackingThread.h
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+++ b/third_party/WebKit/Source/core/workers/WorkerBackingThread.h
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+// 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 WorkerBackingThread_h
+#define WorkerBackingThread_h
+
+#include "core/CoreExport.h"
+#include "wtf/Forward.h"
+#include "wtf/OwnPtr.h"
+#include "wtf/PassOwnPtr.h"
+#include "wtf/ThreadingPrimitives.h"
+#include <v8.h>
+
+namespace blink {
+
+class WebThread;
+class WebThreadSupportingGC;
+
+// WorkerBackingThread represents a WebThread with Oilpan and V8 potentially
+// shared by multiple WebWorker scripts. A WebWorker needs to call attach() when
+// attaching itself to the backing thread, and call detach() when the script
+// no longer needs the thread.
+// A WorkerBackingThread represents a WebThread while a WorkerThread corresponds
+// to a web worker. There is one-to-one correspondence between WorkerThread and
+// WorkerGlobalScope, but multiple WorkerThreads (i.e., multiple
+// WorkerGlobalScopes) can share one WorkerBackingThread.
+class CORE_EXPORT WorkerBackingThread final {
+public:
+    static PassOwnPtr<WorkerBackingThread> create(const char* name) { return adoptPtr(new WorkerBackingThread(name, false)); }
+    static PassOwnPtr<WorkerBackingThread> create(WebThread* thread) { return adoptPtr(new WorkerBackingThread(thread, false)); }
+
+    // These are needed to suppress leak reports. See
+    // https://crbug.com/590802 and https://crbug.com/v8/1428.
+    static PassOwnPtr<WorkerBackingThread> createForTest(const char* name) { return adoptPtr(new WorkerBackingThread(name, true)); }
+    static PassOwnPtr<WorkerBackingThread> createForTest(WebThread* thread) { return adoptPtr(new WorkerBackingThread(thread, true)); }
+
+    ~WorkerBackingThread();
+
+    // attach() and detach() attaches and detaches Oilpan and V8 to / from
+    // the caller worker script, respectively. attach() and detach() increments
+    // and decrements m_workerScriptCount. attach() initializes Oilpan and V8
+    // when m_workerScriptCount is 0. detach() terminates Oilpan and V8 when
+    // m_workerScriptCount is 1. A worker script must not call any function
+    // after calling detach().
+    // They should be called from |this| thread.
+    void attach();
+    void detach();
+
+    unsigned workerScriptCount()
+    {
+        MutexLocker locker(m_mutex);
+        return m_workerScriptCount;
+    }
+
+    WebThreadSupportingGC& backingThread()
+    {
+        ASSERT(m_backingThread);
+        return *m_backingThread;
+    }
+
+    v8::Isolate* isolate() { return m_isolate; }
+
+private:
+    WorkerBackingThread(const char* name, bool shouldCallGCOnShutdown);
+    WorkerBackingThread(WebThread*, bool shouldCallGCOnSHutdown);
+    void initialize();
+    void shutdown();
+
+    // Protects |m_workerScriptCount|.
+    Mutex m_mutex;
+    OwnPtr<WebThreadSupportingGC> m_backingThread;
+    v8::Isolate* m_isolate = nullptr;
+    unsigned m_workerScriptCount = 0;
+    bool m_isOwningThread;
+    bool m_shouldCallGCOnShutdown;
+};
+
+} // namespace blink
+
+#endif // WorkerBackingThread_h