Add PrerenderUnload browser test

chrome/browser/prerender/prerender_manager.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_manager.h"
 
 #include <string>
 
 #include "base/logging.h"
 #include "base/metrics/field_trial.h"
@@ skipping 62 matching lines @@
 class PrerenderManager::OnCloseTabContentsDeleter : public TabContentsDelegate {
  public:
   OnCloseTabContentsDeleter(PrerenderManager* manager,
                             TabContentsWrapper* tab)
       : manager_(manager),
         tab_(tab) {
     tab_->tab_contents()->set_delegate(this);
   }
 
   virtual void CloseContents(TabContents* source) OVERRIDE {
+    tab_->tab_contents()->set_delegate(NULL);
     manager_->ScheduleDeleteOldTabContents(tab_.release(), this);
   }
 
   virtual bool ShouldSuppressDialogs() OVERRIDE {
     return true;
   }
 
   // TabContentsDelegate implementation (pure virtual methods). Since we are
   // waiting for the tab to close, none of this matters.
   virtual void OpenURLFromTab(TabContents*, const GURL&, const GURL&,
@@ skipping 883 matching lines @@
     ScopedVector<OnCloseTabContentsDeleter>::iterator i = std::find(
         on_close_tab_contents_deleters_.begin(),
         on_close_tab_contents_deleters_.end(),
         deleter);
     DCHECK(i != on_close_tab_contents_deleters_.end());
     on_close_tab_contents_deleters_.erase(i);
   }
 }
 
 }  // namespace prerender