Add field to monitor last visited time for each search engine

components/search_engines/default_search_manager.cc

Index: components/search_engines/default_search_manager.cc
diff --git a/components/search_engines/default_search_manager.cc b/components/search_engines/default_search_manager.cc
index b7fd42847b3d9878eb9238e496c5a446e2cda48a..f7b4740deb125b1fd32f2b32babc218339475b97 100644
--- a/components/search_engines/default_search_manager.cc
+++ b/components/search_engines/default_search_manager.cc
@@ -70,6 +70,7 @@ const char DefaultSearchManager::kInputEncodings[] = "input_encodings";
 
 const char DefaultSearchManager::kDateCreated[] = "date_created";
 const char DefaultSearchManager::kLastModified[] = "last_modified";
+const char DefaultSearchManager::kLastVisited[] = "last_visited";
 
 const char DefaultSearchManager::kUsageCount[] = "usage_count";
 const char DefaultSearchManager::kAlternateURLs[] = "alternate_urls";
@@ -161,6 +162,7 @@ void DefaultSearchManager::SetUserSelectedDefaultSearchEngine(
     NotifyObserver();
     return;
   }
+
   pref_service_->Set(kDefaultSearchProviderDataPrefName,
                      *TemplateURLDataToDictionary(data));
 }
@@ -232,6 +234,7 @@ void DefaultSearchManager::MergePrefsDataWithPrepopulated() {
     engine->sync_guid = prefs_default_search_->sync_guid;
     engine->date_created = prefs_default_search_->date_created;
     engine->last_modified = prefs_default_search_->last_modified;
+    engine->last_visited = prefs_default_search_->last_visited;
 
     prefs_default_search_ = std::move(engine);
     return;