Invoke WorkerScriptLoader's m_finishedCallback callback safely.

Source/web/WebEmbeddedWorkerImpl.cpp

 /*
  * Copyright (C) 2013 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:
  *
  *     * Redistributions of source code must retain the above copyright
  * notice, this list of conditions and the following disclaimer.
  *     * Redistributions in binary form must reproduce the above
@@ skipping 287 matching lines @@
     m_loadingShadowPage = false;
     m_networkProvider = adoptPtr(m_workerContextClient->createServiceWorkerNetworkProvider(frame->dataSource()));
     m_mainScriptLoader = adoptPtr(new WorkerScriptLoader());
     m_mainScriptLoader->setRequestContext(WebURLRequest::RequestContextServiceWorker);
     m_mainScriptLoader->loadAsynchronously(
         *m_mainFrame->frame()->document(),
         m_workerStartData.scriptURL,
         DenyCrossOriginRequests,
         nullptr,
         bind(&WebEmbeddedWorkerImpl::onScriptLoaderFinished, this));
+    // Do nothing here since onScriptLoaderFinished() might be already invoked

[haraken, 2015/07/02 06:18:06]

might be => might have been

[Takashi Toyoshima, 2015/07/02 07:33:56]

Oops, tense is so important here.

+    // and |this| might have been deleted at this point.
 }
 
 void WebEmbeddedWorkerImpl::sendProtocolMessage(int callId, const WebString& message, const WebString& state)
 {
     m_workerContextClient->sendDevToolsMessage(callId, message, state);
 }
 
 void WebEmbeddedWorkerImpl::resumeStartup()
 {
     WaitingForDebuggerState waitingForDebuggerState = m_waitingForDebuggerState;
@@ skipping 67 matching lines @@
     m_mainScriptLoader.clear();
 
     m_workerGlobalScopeProxy = ServiceWorkerGlobalScopeProxy::create(*this, *document, *m_workerContextClient);
     m_loaderProxy = WorkerLoaderProxy::create(this);
     m_workerThread = ServiceWorkerThread::create(m_loaderProxy, *m_workerGlobalScopeProxy);
     m_workerThread->start(startupData.release());
     m_workerInspectorProxy->workerThreadCreated(document, m_workerThread.get(), scriptURL);
 }
 
 } // namespace blink