Revert of [Blink-WebWorkers] WorkerSharedTimer cancels extra delayed tasks.

Source/core/workers/WorkerThread.cpp

Index: Source/core/workers/WorkerThread.cpp
diff --git a/Source/core/workers/WorkerThread.cpp b/Source/core/workers/WorkerThread.cpp
index 6a4ba101005434cbe96cdc2f9389af5082bb8e4a..166679e448d1e49897a71187389409c8dec51f31 100644
--- a/Source/core/workers/WorkerThread.cpp
+++ b/Source/core/workers/WorkerThread.cpp
@@ -85,39 +85,12 @@
     return workerThreads().size();
 }
 
-class WorkerThreadCancelableTask FINAL : public ExecutionContextTask {
-    WTF_MAKE_NONCOPYABLE(WorkerThreadCancelableTask); WTF_MAKE_FAST_ALLOCATED;
-public:
-    static PassOwnPtr<WorkerThreadCancelableTask> create(const Closure& closure)
-    {
-        return adoptPtr(new WorkerThreadCancelableTask(closure));
-    }
-
-    virtual void performTask(ExecutionContext*) OVERRIDE
-    {
-        if (!m_taskCanceled)
-            m_closure();
-    }
-
-    void cancelTask() { m_taskCanceled = true; }
-
-private:
-    explicit WorkerThreadCancelableTask(const Closure& closure)
-    : m_closure(closure)
-    , m_taskCanceled(false)
-    { }
-
-    Closure m_closure;
-    bool m_taskCanceled;
-};
-
 class WorkerSharedTimer : public SharedTimer {
 public:
     explicit WorkerSharedTimer(WorkerThread* workerThread)
         : m_workerThread(workerThread)
         , m_nextFireTime(0.0)
         , m_running(false)
-        , m_lastQueuedTask(0)
     { }
 
     typedef void (*SharedTimerFunction)();
@@ -143,21 +116,12 @@
 
         m_running = true;
         m_nextFireTime = currentTime() + interval;
-
-        if (m_lastQueuedTask)
-            m_lastQueuedTask->cancelTask();
-
-        // Now queue the task as a cancellable one.
-        m_lastQueuedTask = WorkerThreadCancelableTask::create(bind(&WorkerSharedTimer::OnTimeout, this)).leakPtr();
-        m_workerThread->postDelayedTask(adoptPtr(m_lastQueuedTask), delay);
+        m_workerThread->postDelayedTask(createSameThreadTask(&WorkerSharedTimer::OnTimeout, this), delay);
     }
 
     virtual void stop()
     {
         m_running = false;
-        if (m_lastQueuedTask)
-            m_lastQueuedTask->cancelTask();
-        m_lastQueuedTask = 0;
     }
 
     double nextFireTime() { return m_nextFireTime; }
@@ -166,9 +130,6 @@
     void OnTimeout()
     {
         ASSERT(m_workerThread->workerGlobalScope());
-
-        m_lastQueuedTask = 0;
-
         if (m_sharedTimerFunction && m_running && !m_workerThread->workerGlobalScope()->isClosing())
             m_sharedTimerFunction();
     }
@@ -177,7 +138,6 @@
     SharedTimerFunction m_sharedTimerFunction;
     double m_nextFireTime;
     bool m_running;
-    WorkerThreadCancelableTask* m_lastQueuedTask;
 };
 
 class WorkerThreadTask : public blink::WebThread::Task {