Change behaivor to decide whether a search engine should be shown in the default list

components/search_engines/default_search_manager.cc

 // Copyright 2014 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 "components/search_engines/default_search_manager.h"
 
 #include <stddef.h>
 #include <stdint.h>
 
 #include <algorithm>
@@ skipping 380 matching lines @@
         prefs_default_search_->input_encodings.push_back(encoding);
     }
   }
 
   url_dict->GetString(kSearchTermsReplacementKey,
                       &prefs_default_search_->search_terms_replacement_key);
 
   url_dict->GetBoolean(kCreatedByPolicy,
                        &prefs_default_search_->created_by_policy);
 
-  prefs_default_search_->show_in_default_list = true;
   MergePrefsDataWithPrepopulated();
 }
 
 void DefaultSearchManager::LoadPrepopulatedDefaultSearch() {
   std::unique_ptr<TemplateURLData> data =
       TemplateURLPrepopulateData::GetPrepopulatedDefaultSearch(pref_service_);
   fallback_default_search_ = std::move(data);
   MergePrefsDataWithPrepopulated();
 }
 
 void DefaultSearchManager::NotifyObserver() {
   if (!change_observer_.is_null()) {
     Source source = FROM_FALLBACK;
     TemplateURLData* data = GetDefaultSearchEngine(&source);
     change_observer_.Run(data, source);
   }
 }