Cleanup: Pass std::string as const reference if possible

chrome/browser/spellchecker/spellcheck_service.h

 // 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.
 
 #ifndef CHROME_BROWSER_SPELLCHECKER_SPELLCHECK_SERVICE_H_
 #define CHROME_BROWSER_SPELLCHECKER_SPELLCHECK_SERVICE_H_
 
 #include <string>
 #include <vector>
 
@@ skipping 93 matching lines @@
 
   // Load a dictionary from a given path. Format specifies how the dictionary
   // is stored. Return value is true if successful.
   bool LoadExternalDictionary(std::string language,
                               std::string locale,
                               std::string path,
                               DictionaryFormat format);
 
   // Unload a dictionary. The path is given to identify the dictionary.
   // Return value is true if successful.
-  bool UnloadExternalDictionary(std::string path);
+  bool UnloadExternalDictionary(const std::string& /* path */);
 
   // NotificationProfile implementation.
   void Observe(int type,
                const content::NotificationSource& source,
                const content::NotificationDetails& details) override;
 
   // SpellcheckCustomDictionary::Observer implementation.
   void OnCustomDictionaryLoaded() override;
   void OnCustomDictionaryChanged(
       const SpellcheckCustomDictionary::Change& dictionary_change) override;
@@ skipping 46 matching lines @@
   ScopedVector<SpellcheckHunspellDictionary> hunspell_dictionaries_;
 
   scoped_ptr<spellcheck::FeedbackSender> feedback_sender_;
 
   base::WeakPtrFactory<SpellcheckService> weak_ptr_factory_;
 
   DISALLOW_COPY_AND_ASSIGN(SpellcheckService);
 };
 
 #endif  // CHROME_BROWSER_SPELLCHECKER_SPELLCHECK_SERVICE_H_