workers: Move ownership of WebThread from WorkerThread

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..41f10d99fbf559c244e9e33ee1039fca6e795f8d 100644
--- a/Source/core/workers/WorkerThread.h
+++ b/Source/core/workers/WorkerThread.h
@@ -64,7 +64,7 @@ public:
     virtual void start();
     virtual void stop();
 
-    virtual PassOwnPtr<WebThreadSupportingGC> createWebThreadSupportingGC();
+    virtual WebThreadSupportingGC* webThreadSupportingGC() = 0;

[kinuko, 2015/04/30 02:30:07]

Can you give a brief explanation? It'd be nice to cover that: 1. it may create a
new thread on first access, and also 2. some implementation may reuse the
backing thread for multiple WorkerThread instance while most others do
one-to-one mapping.

[sadrul, 2015/04/30 05:27:40]

Done.

     virtual void didStartRunLoop();
     virtual void didStopRunLoop();
 
@@ -110,7 +110,7 @@ public:
     void setWorkerInspectorController(WorkerInspectorController*);
 
 protected:
-    WorkerThread(const char* threadName, PassRefPtr<WorkerLoaderProxy>, WorkerReportingProxy&, PassOwnPtr<WorkerThreadStartupData>);
+    WorkerThread(PassRefPtr<WorkerLoaderProxy>, WorkerReportingProxy&, PassOwnPtr<WorkerThreadStartupData>);
 
     // Factory method for creating a new worker context for the thread.
     virtual PassRefPtrWillBeRawPtr<WorkerGlobalScope> createWorkerGlobalScope(PassOwnPtr<WorkerThreadStartupData>) = 0;
@@ -135,7 +135,6 @@ private:
     void postDelayedTask(PassOwnPtr<ExecutionContextTask>, long long delayMs);
     void postDelayedTask(const WebTraceLocation&, PassOwnPtr<ExecutionContextTask>, long long delayMs);
 
-    const char* m_threadName;
     bool m_terminated;
     MessageQueue<WorkerThreadTask> m_debuggerMessageQueue;
     OwnPtr<WebThread::TaskObserver> m_microtaskRunner;
@@ -159,12 +158,7 @@ private:
     // Used to signal thread termination.
     OwnPtr<WebWaitableEvent> m_terminationEvent;
 
-    // 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
-    // no pending tasks on the thread might want to access any of the other
-    // members during the WorkerThread's destruction.
-    OwnPtr<WebThreadSupportingGC> m_thread;
+    WebThreadSupportingGC* m_thread;
 };
 
 } // namespace blink