Make WorkerScriptLoader back to RefCounted class

Source/core/workers/WorkerScriptLoader.cpp

 /*
  * Copyright (C) 2009 Apple Inc. All Rights Reserved.
  * Copyright (C) 2009, 2011 Google Inc. All Rights Reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  * 1. Redistributions of source code must retain the above copyright
  *    notice, this list of conditions and the following disclaimer.
  * 2. Redistributions in binary form must reproduce the above copyright
@@ skipping 82 matching lines @@
     OwnPtr<ResourceRequest> request(createResourceRequest());
     if (!request)
         return;
 
     ThreadableLoaderOptions options;
     options.crossOriginRequestPolicy = crossOriginRequestPolicy;
 
     ResourceLoaderOptions resourceLoaderOptions;
     resourceLoaderOptions.allowCredentials = AllowStoredCredentials;
 
+    // During create, callbacks may happen which could remove the last reference
+    // to this object, while some of the callchain assumes that the client and
+    // loader wouldn't be deleted within callbacks.
+    // (E.g. see crbug.com/524694 for why we can't easily remove this protect)
+    RefPtr<WorkerScriptLoader> protect(this);
     m_needToCancel = true;
     m_threadableLoader = ThreadableLoader::create(executionContext, this, *request, options, resourceLoaderOptions);
     if (m_failed)
         notifyFinished();
-    // Do nothing here since notifyFinished() could delete |this|.
 }
 
 const KURL& WorkerScriptLoader::responseURL() const
 {
     ASSERT(!failed());
     return m_responseURL;
 }
 
 PassOwnPtr<ResourceRequest> WorkerScriptLoader::createResourceRequest()
 {
@@ skipping 107 matching lines @@
     // document (which is implemented in WorkerMessagingProxy, and
     // m_contentSecurityPolicy should be left as nullptr to inherit the policy).
     if (!response.url().protocolIs("blob") && !response.url().protocolIs("file") && !response.url().protocolIs("filesystem")) {
         m_contentSecurityPolicy = ContentSecurityPolicy::create();
         m_contentSecurityPolicy->setOverrideURLForSelf(response.url());
         m_contentSecurityPolicy->didReceiveHeaders(ContentSecurityPolicyResponseHeaders(response));
     }
 }
 
 } // namespace blink