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 d9bd49b952000d06cc50138b92223b7815c46e40..7f1058ff12af7eba1ede46341e2b8e315af14aa1 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;
@@ -98,8 +97,13 @@ public:
     void willEnterNestedLoop();
     void didLeaveNestedLoop();
 
+    // Prevent execution of all non-shutdown tasks.
+    void preShutdown();
+
     WorkerGlobalScope* workerGlobalScope() const { return m_workerGlobalScope.get(); }
-    bool terminated();
+
+    // Virtual for testing.
+    virtual bool terminated();
 
     // Number of active worker threads.
     static unsigned workerThreadCount();
@@ -122,8 +126,21 @@ protected:
     virtual void destroyIsolate();
     virtual void terminateV8Execution();
 
+    // This is protected virtual for testing.
+    virtual bool doIdleGc(double deadlineSeconds);
+
+    WebScheduler* schedulerForTesting() const
+    {
+        return m_webScheduler;
+    }
+
+    WebThreadSupportingGC* threadForTesting() const
+    {
+        return m_thread.get();
+    }
+
 private:
-    friend class WorkerSharedTimer;
+    friend class WorkerThreadIdleTask;
     friend class WorkerThreadShutdownFinishTask;
 
     void stopInShutdownSequence();
@@ -131,7 +148,7 @@ private:
 
     void initialize();
     void cleanup();
-    void idleHandler();
+    void idleTask(double deadlineSeconds);
     void postDelayedTask(PassOwnPtr<ExecutionContextTask>, long long delayMs);
     void postDelayedTask(const WebTraceLocation&, PassOwnPtr<ExecutionContextTask>, long long delayMs);
 
@@ -159,6 +176,11 @@ private:
     // Used to signal thread termination.
     OwnPtr<WebWaitableEvent> m_terminationEvent;
 
+    RawPtr<WebScheduler> m_webScheduler; // NOT OWNED.
+
+    Mutex m_preShutdownMutex;
+    bool m_preShutdown;
+
     // 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