Introduce WorkerBackingThread

third_party/WebKit/Source/core/workers/WorkerBackingThread.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 WorkerBackingThread_h
+#define WorkerBackingThread_h
+
+#include "core/CoreExport.h"
+#include "wtf/Forward.h"
+#include "wtf/OwnPtr.h"
+#include "wtf/PassOwnPtr.h"
+#include "wtf/PassRefPtr.h"
+#include "wtf/RefCounted.h"
+#include "wtf/ThreadingPrimitives.h"
+#include <v8.h>
+
+namespace blink {
+
+class WebThread;
+class WebThreadSupportingGC;
+
+// Ref counting must be done in the main thread.
+class CORE_EXPORT WorkerBackingThread final : public RefCounted<WorkerBackingThread> {
+public:
+    static PassRefPtr<WorkerBackingThread> create(const char* name) { return adoptRef(new WorkerBackingThread(name, false)); }
+    static PassRefPtr<WorkerBackingThread> create(WebThread* thread) { return adoptRef(new WorkerBackingThread(thread, false)); }
+
+    // These are needed to suppress leak reports. See
+    // https://crbug.com/590802 and https://crbug.com/v8/1428.
+    static PassRefPtr<WorkerBackingThread> createForTest(const char* name) { return adoptRef(new WorkerBackingThread(name, true)); }
+    static PassRefPtr<WorkerBackingThread> createForTest(WebThread* thread) { return adoptRef(new WorkerBackingThread(thread, true)); }
+
+    ~WorkerBackingThread();
+
+    void attach();
+    void detach();

[kinuko, 2016/03/30 16:03:05]

nit: please have comments for attach/detach

[yhirano, 2016/03/31 08:29:11]

Done.

+    unsigned workerScriptCount()
+    {
+        MutexLocker locker(m_mutex);
+        return m_workerScriptCount;
+    }
+
+    WebThreadSupportingGC& backingThread()
+    {
+        ASSERT(m_backingThread);
+        return *m_backingThread;
+    }
+
+    v8::Isolate* isolate() const { return m_isolate; }

[kinuko, 2016/03/30 16:03:05]

This pattern seems to have exist before your change, but returning non-const
pointer from const method is not recommended

[yhirano, 2016/03/31 08:29:11]

That's funny, some reviewers prefer it and I was once told to put const for such
an interface :(

[kinuko, 2016/03/31 09:10:11]

https://google.github.io/styleguide/cppguide.html#Use_of_const
"Declare methods to be const whenever possible. Accessors should almost always
be const. Other methods should be const if they do not modify any data members,
do not call any non-const methods, and do not return a non-const pointer or
non-const reference to a data member."

Putting const is definitely preferred but if all these conditions apply.

+
+private:
+    explicit WorkerBackingThread(const char* name, bool shouldCallGCOnShutdown);
+    explicit WorkerBackingThread(WebThread*, bool shouldCallGCOnSHutdown);

[kinuko, 2016/03/30 16:03:05]

nit: no need of explicit

[yhirano, 2016/03/31 08:29:11]

Done.

+    void initialize();
+    void shutdown();
+
+    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