Fix a crash when dns prefetching was being shut down without being started....

chrome/browser/browser_process_impl.cc

 // Copyright (c) 2006-2008 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "chrome/browser/browser_process_impl.h"
 
 #include "base/command_line.h"
 #include "base/path_service.h"
 #include "base/thread.h"
 #include "base/waitable_event.h"
@@ skipping 160 matching lines @@
     if (resource_dispatcher_host()->safe_browsing_service())
       resource_dispatcher_host()->safe_browsing_service()->ShutDown();
 
     // Cancel pending requests and prevent new requests.
     resource_dispatcher_host()->Shutdown();
   }
 
   // Shutdown DNS prefetching now to ensure that network stack objects
   // living on the IO thread get destroyed before the IO thread goes away.
   io_thread_->message_loop()->PostTask(FROM_HERE,
-      NewRunnableFunction(chrome_browser_net::ShutdownDnsPrefetch));
+      NewRunnableFunction(chrome_browser_net::EnsureDnsPrefetchShutdown));
 
   // Need to stop io_thread_ before resource_dispatcher_host_, since
   // io_thread_ may still deref ResourceDispatcherHost and handle resource
   // request before going away.
   io_thread_.reset();
 
   // Clean up state that lives on the file_thread_ before it goes away.
   if (resource_dispatcher_host_.get()) {
     resource_dispatcher_host()->download_file_manager()->Shutdown();
     resource_dispatcher_host()->save_file_manager()->Shutdown();
@@ skipping 194 matching lines @@
   // TODO(port): remove this completely, it has no business being here.
 #endif
 }
 
 void BrowserProcessImpl::CreateGoogleURLTracker() {
   DCHECK(google_url_tracker_.get() == NULL);
   scoped_ptr<GoogleURLTracker> google_url_tracker(new GoogleURLTracker);
   google_url_tracker_.swap(google_url_tracker);
 }