compositor-worker: Share a thread and an isolate for compositor workers.

Source/modules/compositorworker/CompositorWorkerManager.cpp

Index: Source/modules/compositorworker/CompositorWorkerManager.cpp
diff --git a/Source/modules/compositorworker/CompositorWorkerManager.cpp b/Source/modules/compositorworker/CompositorWorkerManager.cpp
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index 0000000000000000000000000000000000000000..dc7fd62952dbcae3837c6ab1c628aa83409e4ddd
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+++ b/Source/modules/compositorworker/CompositorWorkerManager.cpp
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+// Copyright 2015 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.
+
+#include "config.h"
+#include "modules/compositorworker/CompositorWorkerManager.h"
+
+#include "platform/ThreadSafeFunctional.h"
+#include "platform/WebThreadSupportingGC.h"
+#include "wtf/MainThread.h"
+#include "wtf/ThreadingPrimitives.h"
+
+namespace blink {
+
+namespace {
+
+class SharedV8Isolate final : public WorkerIsolateWrapper {
+    WTF_MAKE_NONCOPYABLE(SharedV8Isolate);
+public:
+    explicit SharedV8Isolate(v8::Isolate* isolate)
+        : m_isolate(isolate) { }
+    ~SharedV8Isolate() override
+    {
+        CompositorWorkerManager::instance()->destroyIsolate();
+    }
+
+private:
+    // WorkerIsolateWrapper:
+    v8::Isolate* isolate() const override { return m_isolate; }
+    void willDestroy() override
+    {
+        CompositorWorkerManager::instance()->willDestroyIsolate();
+    }
+
+    void terminateExecution() override
+    {
+        CompositorWorkerManager::instance()->terminateIsolate();
+    }
+
+    v8::Isolate* m_isolate;
+};
+
+static CompositorWorkerManager* s_instance = nullptr;
+
+static Mutex& singletonMutex()
+{
+    AtomicallyInitializedStaticReference(Mutex, mutex, new Mutex);
+    return mutex;
+}
+
+static void destroyThread(WebThreadSupportingGC* thread)
+{
+    delete thread;
+}
+
+} // namespace
+
+void CompositorWorkerManager::initialize()
+{
+    MutexLocker lock(singletonMutex());
+    ASSERT(!s_instance);
+    s_instance = new CompositorWorkerManager();
+}
+
+void CompositorWorkerManager::shutdown()
+{
+    MutexLocker lock(singletonMutex());
+    ASSERT(s_instance);
+    delete s_instance;
+    s_instance = nullptr;
+}
+
+CompositorWorkerManager* CompositorWorkerManager::instance()
+{
+    MutexLocker lock(singletonMutex());
+    ASSERT(s_instance);
+    return s_instance;
+}
+
+CompositorWorkerManager::CompositorWorkerManager()
+{
+}
+
+CompositorWorkerManager::~CompositorWorkerManager()
+{
+}
+
+WebThreadSupportingGC& CompositorWorkerManager::compositorWorkerThread()
+{
+    MutexLocker lock(m_mutex);
+    if (!m_thread) {
+        ASSERT(isMainThread());
+        ASSERT(!m_workerCount);
+        m_thread = WebThreadSupportingGC::create("CompositorWorker Thread");
+    }
+    return *m_thread.get();
+}
+
+void CompositorWorkerManager::initializeBackingThread()
+{
+    ASSERT(m_thread->isCurrentThread());
+    MutexLocker lock(m_mutex);
+    ++m_workerCount;
+    if (m_workerCount == 1)
+        m_thread->initialize();
+}
+
+void CompositorWorkerManager::shutdownBackingThread()
+{
+    MutexLocker lock(m_mutex);
+    ASSERT(m_thread->isCurrentThread());
+    ASSERT(m_workerCount > 0);
+    --m_workerCount;
+    if (m_workerCount == 0) {
+        m_thread->shutdown();
+        Platform::current()->mainThread()->postTask(FROM_HERE, threadSafeBind(destroyThread, AllowCrossThreadAccess(m_thread.leakPtr())));
+    }
+}
+
+PassOwnPtr<WorkerIsolateWrapper> CompositorWorkerManager::createIsolate()
+{
+    MutexLocker lock(m_mutex);
+    ASSERT(m_thread->isCurrentThread());
+    if (!m_isolate)
+        m_isolate = WorkerIsolateWrapper::createDefault();
+    // It is safe to use the existing isolate even if TerminateExecution() has been
+    // called on it, without calling CancelTerminateExecution().
+    return adoptPtr(new SharedV8Isolate(m_isolate->isolate()));
+}
+
+void CompositorWorkerManager::willDestroyIsolate()
+{
+    MutexLocker lock(m_mutex);
+    ASSERT(m_thread->isCurrentThread());
+    if (m_workerCount == 1)
+        m_isolate->willDestroy();
+}
+
+void CompositorWorkerManager::destroyIsolate()
+{
+    MutexLocker lock(m_mutex);
+    if (!m_thread) {
+        ASSERT(m_workerCount == 0);
+        m_isolate.clear();
+    }
+}
+
+void CompositorWorkerManager::terminateIsolate()
+{
+    MutexLocker lock(m_mutex);
+    ASSERT(isMainThread());
+    if (m_workerCount > 1)
+        return;
+
+    m_isolate->terminateExecution();
+}
+
+} // namespace blink