Turn WorkerLoaderProxy into a threadsafe, ref-counted object.

Source/core/workers/SharedWorkerThread.h

Index: Source/core/workers/SharedWorkerThread.h
diff --git a/Source/core/workers/SharedWorkerThread.h b/Source/core/workers/SharedWorkerThread.h
index 34e84ef2d92dadca37d301f7dbecc4f9bf037f14..672cbe8c2250b1c8aea1aed0ccce10eba74ed734 100644
--- a/Source/core/workers/SharedWorkerThread.h
+++ b/Source/core/workers/SharedWorkerThread.h
@@ -39,14 +39,14 @@ class WorkerThreadStartupData;
 
 class SharedWorkerThread : public WorkerThread {
 public:
-    static PassRefPtr<SharedWorkerThread> create(const String& name, WorkerLoaderProxy&, WorkerReportingProxy&, PassOwnPtrWillBeRawPtr<WorkerThreadStartupData>);
+    static PassRefPtr<SharedWorkerThread> create(const String& name, PassRefPtr<WorkerLoaderProxy>, WorkerReportingProxy&, PassOwnPtrWillBeRawPtr<WorkerThreadStartupData>);
     virtual ~SharedWorkerThread();
 
 protected:
     virtual PassRefPtrWillBeRawPtr<WorkerGlobalScope> createWorkerGlobalScope(PassOwnPtrWillBeRawPtr<WorkerThreadStartupData>) override;
 
 private:
-    SharedWorkerThread(const String& name, WorkerLoaderProxy&, WorkerReportingProxy&, PassOwnPtrWillBeRawPtr<WorkerThreadStartupData>);
+    SharedWorkerThread(const String& name, PassRefPtr<WorkerLoaderProxy>, WorkerReportingProxy&, PassOwnPtrWillBeRawPtr<WorkerThreadStartupData>);
 
     String m_name;
 };