Fix potential crash in WebEmbeddedWorkerImpl

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 200 matching lines @@
         toWebFrameImpl(m_mainFrame)->frame()->document(),
         m_workerStartData.scriptURL,
         bind(&WebEmbeddedWorkerImpl::onScriptLoaderFinished, this));
 }
 
 void WebEmbeddedWorkerImpl::onScriptLoaderFinished()
 {
     ASSERT(m_mainScriptLoader);
 
     if (m_mainScriptLoader->failed() || m_askedToTerminate) {
+        m_mainScriptLoader.clear();
+        // This may delete 'this'.
         m_workerContextClient->workerContextFailedToStart();
-        m_mainScriptLoader.clear();
         return;
     }
 
     WorkerThreadStartMode startMode =
         (m_workerStartData.startMode == WebEmbeddedWorkerStartModePauseOnStart)
         ? PauseWorkerGlobalScopeOnStart : DontPauseWorkerGlobalScopeOnStart;
 
     // This is to be owned by ServiceWorker's WorkerGlobalScope, and is
     // guaranteed to be around while the WorkerGlobalScope is alive.
     WebServiceWorkerContextClient* contextClient = m_workerContextClient.get();
@@ skipping 16 matching lines @@
     m_mainScriptLoader.clear();
 
     m_workerGlobalScopeProxy = ServiceWorkerGlobalScopeProxy::create(*this, *toWebFrameImpl(m_mainFrame)->frame()->document(), *contextClient);
     m_loaderProxy = LoaderProxy::create(*this);
 
     m_workerThread = ServiceWorkerThread::create(*m_loaderProxy, *m_workerGlobalScopeProxy, startupData.release());
     m_workerThread->start();
 }
 
 } // namespace blink