Refactor TimeBase to post tasks. Workers to use real Idle tasks.

Source/core/workers/WorkerThread.h

Index: Source/core/workers/WorkerThread.h
diff --git a/Source/core/workers/WorkerThread.h b/Source/core/workers/WorkerThread.h
index 39d93c824951dfd87c11b73c39c2ec5962613621..3934121f27f9162113013b67705a00bce1427b10 100644
--- a/Source/core/workers/WorkerThread.h
+++ b/Source/core/workers/WorkerThread.h
@@ -47,7 +47,6 @@ class WebWaitableEvent;
 class WorkerGlobalScope;
 class WorkerInspectorController;
 class WorkerReportingProxy;
-class WorkerSharedTimer;
 class WorkerThreadShutdownFinishTask;
 class WorkerThreadStartupData;
 class WorkerThreadTask;
@@ -118,7 +117,6 @@ protected:
     virtual void postInitialize() { }
 
 private:
-    friend class WorkerSharedTimer;
     friend class WorkerThreadShutdownFinishTask;
 
     void stopInShutdownSequence();
@@ -133,7 +131,6 @@ private:
     void terminateV8Execution();
 
     bool m_terminated;
-    OwnPtr<WorkerSharedTimer> m_sharedTimer;
     MessageQueue<WorkerThreadTask> m_debuggerMessageQueue;
     OwnPtr<WebThread::TaskObserver> m_microtaskRunner;