Introduce a basic Blink Scheduler

Source/platform/scheduler/Scheduler.h

Index: Source/platform/scheduler/Scheduler.h
diff --git a/Source/platform/scheduler/Scheduler.h b/Source/platform/scheduler/Scheduler.h
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+/*
+ * Copyright (C) 2014 Google Inc. All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY APPLE INC. AND ITS CONTRIBUTORS ``AS IS''
+ * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO,
+ * THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
+ * PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL APPLE INC. OR ITS CONTRIBUTORS
+ * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
+ * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
+ * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
+ * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
+ * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
+ * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF
+ * THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#ifndef Scheduler_h
+#define Scheduler_h
+
+#include "platform/PlatformExport.h"
+#include "public/platform/WebThread.h"
+#include "wtf/Functional.h"
+#include "wtf/Noncopyable.h"
+#include "wtf/PassOwnPtr.h"
+#include "wtf/ThreadingPrimitives.h"
+#include <deque>
+
+namespace WebCore {
+
+class PLATFORM_EXPORT Scheduler {
+    WTF_MAKE_NONCOPYABLE(Scheduler);
+public:
+    static Scheduler* current();
+    static void initializeOnMainThread();
+    static void shutdown();
+
+    // Schedule a generic task to be run on the blink main thread. Takes
+    // ownership of |Task|. Can be called from any thread.
+    void postTask(blink::WebThread::Task*);
+
+    // Schedule an input processing task to be run on the blink main thread.
+    // Takes ownership of |Task|. Can be called from any thread.
+    void postInputTask(blink::WebThread::Task*);
+
+    // Schedule a compositor task to run on the blink main thread. Takes
+    // ownership of |Task|. Can be called from any thread.
+    void postCompositorTask(blink::WebThread::Task*);
+
+    // Schedule a BeginFrame task to run on the blink main thread. Takes
+    // ownership of |Task|. Can be called from any thread. Maintains ordering
+    // with other compositor tasks.
+    void postBeginFrameTask(blink::WebThread::Task*, double frameTime, double deadline, double interval);
+
+    void setSharedTimerFiredFunction(void (*function)());
+    void setSharedTimerFireInterval(double interval);
+    void stopSharedTimer();
+
+    bool shouldYieldForHighPriorityWork();
+
+private:
+    typedef std::deque<blink::WebThread::Task*> TaskQueue;
+
+    Scheduler();
+    ~Scheduler();
+
+    void scheduleTask(TaskQueue*, blink::WebThread::Task*);
+    PassOwnPtr<blink::WebThread::Task> chooseNextTask();
+    void runScheduledTasks();
+
+    static void sharedTimerAdapter();
+    void runSharedTimer();
+
+    static Scheduler* s_currentScheduler;
+    blink::WebThread* m_mainThread;
+
+    void (*m_sharedTimerFunction)();
+
+    Mutex m_taskQueueLock;
+    TaskQueue m_pendingInputTasks;
+    TaskQueue m_pendingCompositorTasks;
+    TaskQueue m_pendingTasks;
+    bool m_workScheduled;
+    bool m_hasPendingBeginFrameTask;
+};
+
+} // namespace WebCore
+
+#endif // Scheduler_h