Coverity: Pass parameters by reference.

chrome/browser/sync/glue/preference_model_associator.cc

 // 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.
 
 #include "chrome/browser/sync/glue/preference_model_associator.h"
 
 #include "base/json/json_reader.h"
 #include "base/logging.h"
 #include "base/values.h"
 #include "base/utf_string_conversions.h"
@@ skipping 148 matching lines @@
     return false;
   }
 
   // The sync model has user created nodes if the preferences folder has any
   // children.
   *has_nodes = sync_api::kInvalidId != preferences_node.GetFirstChildId();
   return true;
 }
 
 int64 PreferenceModelAssociator::GetSyncIdFromChromeId(
-    const std::string preference_name) {
+    const std::string& preference_name) {
   PreferenceNameToSyncIdMap::const_iterator iter =
       id_map_.find(preference_name);
   return iter == id_map_.end() ? sync_api::kInvalidId : iter->second;
 }
 
 void PreferenceModelAssociator::Associate(
     const PrefService::Preference* preference, int64 sync_id) {
   DCHECK(BrowserThread::CurrentlyOn(BrowserThread::UI));
   DCHECK_NE(sync_api::kInvalidId, sync_id);
   DCHECK(id_map_.find(preference->name()) == id_map_.end());
@@ skipping 127 matching lines @@
   // notification to update the UI.
   if (0 == pref_name.compare(prefs::kShowBookmarkBar)) {
     NotificationService::current()->Notify(
         NotificationType::BOOKMARK_BAR_VISIBILITY_PREF_CHANGED,
         Source<PreferenceModelAssociator>(this),
         NotificationService::NoDetails());
   }
 }
 
 }  // namespace browser_sync