Fix issues when PrerenderContents::Destroy() is called during TabContents destruction.

chrome/browser/prerender/prerender_contents.cc

 // Copyright (c) 2011 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/prerender/prerender_contents.h"
 
 #include <algorithm>
 #include <utility>
 
 #include "base/process_util.h"
@@ skipping 664 matching lines @@
 
 void PrerenderContents::OnRenderViewGone(int status, int exit_code) {
   Destroy(FINAL_STATUS_RENDERER_CRASHED);
 }
 
 void PrerenderContents::DidStopLoading() {
   has_stopped_loading_ = true;
 }
 
 void PrerenderContents::Destroy(FinalStatus final_status) {
-  if (prerender_manager_->IsPendingDelete(this))
+  if (!prerender_manager_->MoveEntryToPendingDelete(this))
     return;
 
-  prerender_manager_->MoveEntryToPendingDelete(this);
   set_final_status(final_status);
   // We may destroy the PrerenderContents before we have initialized the
   // RenderViewHost. Otherwise set the Observer's PrerenderContents to NULL to
   // avoid any more messages being sent.
   if (render_view_host_observer_.get())
     render_view_host_observer_->set_prerender_contents(NULL);
 }
 
 void PrerenderContents::RendererUnresponsive(RenderViewHost* render_view_host,
                                              bool is_during_unload) {
@@ skipping 59 matching lines @@
   //               used.
   if (UseTabContents()) {
     if (!prerender_contents_.get())
       return NULL;
     return prerender_contents_->render_view_host();
   }
   return render_view_host_;
 }
 
 }  // namespace prerender