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 1ac816457ec1767d3193d861ff84a469016d24ca..6c0114ecc25be05f84e0a54248bffe30dfe96a05 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;
@@ -123,15 +122,19 @@ protected:
     virtual void terminateV8Execution();
 
 private:
-    friend class WorkerSharedTimer;
+    friend class WorkerThreadIdleTask;
     friend class WorkerThreadShutdownFinishTask;
+    friend class WorkerThreadWaitUntilIdleTask;
+    friend class WorkerThreadWakeupIdleTask;
 
     void stopInShutdownSequence();
     void stopInternal();
 
     void initialize();
     void cleanup();
-    void idleHandler();
+    void dontStartIdleTaskYet();

[Sami, 2015/04/02 10:59:20]

Should these be talking about the idle period instead of a task?

+    void maybeStartIdleTask();
+    void idleTask(double deadlineSeconds);
     void postDelayedTask(PassOwnPtr<ExecutionContextTask>, long long delayMs);
     void postDelayedTask(const WebTraceLocation&, PassOwnPtr<ExecutionContextTask>, long long delayMs);
 
@@ -158,6 +161,8 @@ private:
     // Used to signal thread termination.
     OwnPtr<WebWaitableEvent> m_terminationEvent;
 
+    bool m_dontStartIdleTaskYet;
+
     // FIXME: This has to be last because of crbug.com/401397 - the
     // WorkerThread might get deleted before it had a chance to properly
     // shut down. By deleting the WebThread first, we can guarantee that