Turn WorkerLoaderProxy into a threadsafe, ref-counted object.

Source/core/loader/WorkerLoaderClientBridge.h

Index: Source/core/loader/WorkerLoaderClientBridge.h
diff --git a/Source/core/loader/WorkerLoaderClientBridge.h b/Source/core/loader/WorkerLoaderClientBridge.h
index 7ea8c86451714b18f3f3ea3c39ba6b60af4dacf3..6dc6d7bc4809200c10af63c42e3d41c87d511776 100644
--- a/Source/core/loader/WorkerLoaderClientBridge.h
+++ b/Source/core/loader/WorkerLoaderClientBridge.h
@@ -45,7 +45,7 @@ class WorkerLoaderProxy;
 // data to the client wrapper on the worker context thread.
 class WorkerLoaderClientBridge : public ThreadableLoaderClient {
 public:
-    static PassOwnPtr<ThreadableLoaderClient> create(PassRefPtr<ThreadableLoaderClientWrapper>, WorkerLoaderProxy&);
+    static PassOwnPtr<ThreadableLoaderClient> create(PassRefPtr<ThreadableLoaderClientWrapper>, PassRefPtr<WorkerLoaderProxy>);
     virtual ~WorkerLoaderClientBridge();
 
     virtual void didSendData(unsigned long long bytesSent, unsigned long long totalBytesToBeSent) override;
@@ -59,13 +59,13 @@ public:
     virtual void didFailRedirectCheck() override;
 
 private:
-    WorkerLoaderClientBridge(PassRefPtr<ThreadableLoaderClientWrapper>, WorkerLoaderProxy&);
+    WorkerLoaderClientBridge(PassRefPtr<ThreadableLoaderClientWrapper>, PassRefPtr<WorkerLoaderProxy>);
 
     // Used on the worker context thread, while its refcounting is done on
     // either thread.
     RefPtr<ThreadableLoaderClientWrapper> m_workerClientWrapper;
 
-    WorkerLoaderProxy& m_loaderProxy;
+    RefPtr<WorkerLoaderProxy> m_loaderProxy;
 };
 
 } // namespace blink