Coverity: Fix pass by value error.

chrome/browser/history/url_index_private_data.cc

 // Copyright (c) 2012 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/history/url_index_private_data.h"
 
 #include <algorithm>
 #include <functional>
 #include <iterator>
 #include <limits>
@@ skipping 1076 matching lines @@
       map_entry->add_title_word_starts(*i);
   }
 }
 
 // Cache Restoring -------------------------------------------------------------
 
 // static
 void URLIndexPrivateData::RestoreFromFileTask(
     const FilePath& file_path,
     scoped_refptr<URLIndexPrivateData> private_data,
-    std::string languages) {
+    const std::string& languages) {
   private_data = URLIndexPrivateData::RestoreFromFile(file_path, languages);
 }
 
 // static
 scoped_refptr<URLIndexPrivateData> URLIndexPrivateData::RestoreFromFile(
     const FilePath& file_path,
     const std::string& languages) {
   base::TimeTicks beginning_time = base::TimeTicks::Now();
   if (!file_util::PathExists(file_path))
     return NULL;
@@ skipping 236 matching lines @@
 }
 
 // static
 bool URLIndexPrivateData::URLSchemeIsWhitelisted(
     const GURL& gurl,
     const std::set<std::string>& whitelist) {
   return whitelist.find(gurl.scheme()) != whitelist.end();
 }
 
 }  // namespace history