Protector adds the default prepopulated engine if it was removed.

chrome/browser/search_engines/template_url_prepopulate_data.h

 // 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.
 
 #ifndef CHROME_BROWSER_SEARCH_ENGINES_TEMPLATE_URL_PREPOPULATE_DATA_H_
 #define CHROME_BROWSER_SEARCH_ENGINES_TEMPLATE_URL_PREPOPULATE_DATA_H_
 #pragma once
 
 #include <stddef.h>
 #include <string>
@@ skipping 17 matching lines @@
 // Loads the set of TemplateURLs from the prepopulate data.  Ownership of the
 // TemplateURLs is passed to the caller.  On return,
 // |default_search_provider_index| is set to the index of the default search
 // provider.
 void GetPrepopulatedEngines(PrefService* prefs,
                             std::vector<TemplateURL*>* t_urls,
                             size_t* default_search_provider_index);
 
 // Returns the default search provider specified by the prepopulate data.
 // The caller owns the returned value, which may be NULL.
+// If |prefs| is NULL, search provider overrides from preferences are not used.
 TemplateURL* GetPrepopulatedDefaultSearch(PrefService* prefs);
 
 // Returns a TemplateURL from the prepopulated data which has the same origin
 // as the given url.  The caller is responsible for deleting the returned
 // TemplateURL.
 TemplateURL* GetEngineForOrigin(PrefService* prefs, const GURL& url_to_find);
 
 // Returns search engine logo for URLs known to have a search engine logo.
 int GetSearchEngineLogo(const GURL& url_to_find);
 
 // Returns the prepopulated search provider whose search URL matches
 // |search_url| or NULL if none is found.  The caller is responsible for
 // deleting the returned TemplateURL.
 TemplateURL* FindPrepopulatedEngine(const std::string& search_url);
 
 }  // namespace TemplateURLPrepopulateData
 
 #endif  // CHROME_BROWSER_SEARCH_ENGINES_TEMPLATE_URL_PREPOPULATE_DATA_H_