avoid dereferencing NULL extension in ExtensionHost

chrome/browser/extensions/extension_service.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/extensions/extension_service.h"
 
 #include <algorithm>
 #include <set>
 
 #include "base/basictypes.h"
@@ skipping 2023 matching lines @@
 
   std::string path_str = UTF16ToUTF8(extension_path.LossyDisplayName());
   std::string message = base::StringPrintf(
       "Could not load extension from '%s'. %s",
       path_str.c_str(), error.c_str());
   ExtensionErrorReporter::GetInstance()->ReportError(message, be_noisy);
 }
 
 void ExtensionService::DidCreateRenderViewForBackgroundPage(
     ExtensionHost* host) {
-  OrphanedDevTools::iterator iter =
-      orphaned_dev_tools_.find(host->extension()->id());
+  OrphanedDevTools::iterator iter = orphaned_dev_tools_.find(host->id());
   if (iter == orphaned_dev_tools_.end())
     return;
 
   DevToolsManager::GetInstance()->AttachClientHost(
       iter->second, host->render_view_host());
   orphaned_dev_tools_.erase(iter);
 }
 
 void ExtensionService::Observe(NotificationType type,
                                const NotificationSource& source,
@@ skipping 147 matching lines @@
 
 ExtensionService::NaClModuleInfoList::iterator
     ExtensionService::FindNaClModule(const GURL& url) {
   for (NaClModuleInfoList::iterator iter = nacl_module_list_.begin();
        iter != nacl_module_list_.end(); ++iter) {
     if (iter->url == url)
       return iter;
   }
   return nacl_module_list_.end();
 }