Nothing is ever added to hosts_to_delete_, so this code does nothing useful.

chrome/browser/search_engines/template_url_model.h

 // Copyright (c) 2010 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.
 
 #ifndef CHROME_BROWSER_SEARCH_ENGINES_TEMPLATE_URL_MODEL_H_
 #define CHROME_BROWSER_SEARCH_ENGINES_TEMPLATE_URL_MODEL_H_
 #pragma once
 
 #include <set>
 
@@ skipping 347 matching lines @@
 
   // Did loading fail? This is only valid if loaded_ is true.
   bool load_failed_;
 
   // If non-zero, we're waiting on a load.
   WebDataService::Handle load_handle_;
 
   // Service used to store entries.
   scoped_refptr<WebDataService> service_;
 
-  // List of hosts to feed to DeleteGeneratedKeywordsMatchingHost. When
-  // we receive NOTIFY_HOST_DELETED_FROM_HISTORY if we haven't loaded yet,
-  // we force a load and add the host to hosts_to_delete_. When done loading
-  // we invoke DeleteGeneratedKeywordsMatchingHost with all the elements of
-  // the vector.
-  std::vector<std::wstring> hosts_to_delete_;
-
   // All visits that occurred before we finished loading. Once loaded
   // UpdateKeywordSearchTermsForURL is invoked for each element of the vector.
   std::vector<history::URLVisitedDetails> visits_to_add_;
 
   const TemplateURL* default_search_provider_;
 
   // Used for UX testing. Gives the slot in the search engine dialog that was
   // chosen as the default search engine.
   int search_engine_dialog_chosen_slot_;
 
   // The default search provider from preferences. This is only valid if
   // GetDefaultSearchProvider is invoked and we haven't been loaded or loading
   // failed. If loading was successful this is not used.
   scoped_ptr<TemplateURL> prefs_default_search_provider_;
 
   // ID assigned to next TemplateURL added to this model. This is an ever
   // increasing integer that is initialized from the database.
   TemplateURL::IDType next_id_;
 
   // List of extension IDs waiting for Load to have keywords registered.
   std::vector<std::string> pending_extension_ids_;
 
   DISALLOW_COPY_AND_ASSIGN(TemplateURLModel);
 };
 
 #endif  // CHROME_BROWSER_SEARCH_ENGINES_TEMPLATE_URL_MODEL_H_