Invoke WorkerScriptLoader's m_finishedCallback callback safely.

Source/core/workers/WorkerScriptLoader.h

 /*
  * 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 36 matching lines @@
 class ExecutionContext;
 class TextResourceDecoder;
 
 class CORE_EXPORT WorkerScriptLoader final : public ThreadableLoaderClient {
     WTF_MAKE_FAST_ALLOCATED(WorkerScriptLoader);
 public:
     WorkerScriptLoader();
     ~WorkerScriptLoader() override;
 
     void loadSynchronously(ExecutionContext&, const KURL&, CrossOriginRequestPolicy);
-    // TODO: finishedCallback is not currently guaranteed to be invoked if used
-    // from worker context and the worker shuts down in the middle of an
+    // TODO: |finishedCallback| is not currently guaranteed to be invoked if
+    // used from worker context and the worker shuts down in the middle of an
     // operation. This will cause leaks when we support nested workers.
+    // Note that callbacks could be invoked before loadAsynchronously() returns.
     void loadAsynchronously(ExecutionContext&, const KURL&, CrossOriginRequestPolicy, PassOwnPtr<Closure> responseCallback, PassOwnPtr<Closure> finishedCallback);
 
-    void notifyError();
-
-    // This will immediately lead to notifyFinished() if loadAsynchronously
+    // This will immediately invoke |finishedCallback| if loadAsynchronously()
     // is in progress.
     void cancel();
 
     String script();
     const KURL& url() const { return m_url; }
     const KURL& responseURL() const;
     bool failed() const { return m_failed; }
     unsigned long identifier() const { return m_identifier; }
     long long appCacheID() const { return m_appCacheID; }
 
     PassOwnPtr<Vector<char>> releaseCachedMetadata() { return m_cachedMetadata.release(); }
     const Vector<char>* cachedMetadata() const { return m_cachedMetadata.get(); }
 
     PassRefPtr<ContentSecurityPolicy> contentSecurityPolicy() { return m_contentSecurityPolicy; }
     PassRefPtr<ContentSecurityPolicy> releaseContentSecurityPolicy() { return m_contentSecurityPolicy.release(); }
 
     // ThreadableLoaderClient
     void didReceiveResponse(unsigned long /*identifier*/, const ResourceResponse&, PassOwnPtr<WebDataConsumerHandle>) override;
     void didReceiveData(const char* data, unsigned dataLength) override;
     void didReceiveCachedMetadata(const char*, int /*dataLength*/) override;
     void didFinishLoading(unsigned long identifier, double) override;
     void didFail(const ResourceError&) override;
     void didFailRedirectCheck() override;
 
     void setRequestContext(WebURLRequest::RequestContext requestContext) { m_requestContext = requestContext; }
 
 private:
     PassOwnPtr<ResourceRequest> createResourceRequest();
+    void notifyError();
     void notifyFinished();
 
     void processContentSecurityPolicy(const ResourceResponse&);
 
     // Callbacks for loadAsynchronously().
     OwnPtr<Closure> m_responseCallback;
     OwnPtr<Closure> m_finishedCallback;
 
     RefPtr<ThreadableLoader> m_threadableLoader;
     String m_responseEncoding;
     OwnPtr<TextResourceDecoder> m_decoder;
     StringBuilder m_script;
     KURL m_url;
     KURL m_responseURL;
     bool m_failed;
     unsigned long m_identifier;
     long long m_appCacheID;
-    bool m_finishing;
     OwnPtr<Vector<char>> m_cachedMetadata;
     WebURLRequest::RequestContext m_requestContext;
     RefPtr<ContentSecurityPolicy> m_contentSecurityPolicy;
 };
 
 } // namespace blink
 
 #endif // WorkerScriptLoader_h