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

chrome/browser/spellchecker/spellcheck_service.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/spellchecker/spellcheck_service.h"
 
 #include "base/logging.h"
 #include "base/prefs/pref_member.h"
 #include "base/prefs/pref_service.h"
 #include "base/strings/string_split.h"
@@ skipping 212 matching lines @@
   return feedback_sender_.get();
 }
 
 bool SpellcheckService::LoadExternalDictionary(std::string language,
                                                std::string locale,
                                                std::string path,
                                                DictionaryFormat format) {
   return false;
 }
 
-bool SpellcheckService::UnloadExternalDictionary(std::string path) {
+bool SpellcheckService::UnloadExternalDictionary(
+    const std::string& /* path */) {
   return false;
 }
 
 void SpellcheckService::Observe(int type,
                                 const content::NotificationSource& source,
                                 const content::NotificationDetails& details) {
   DCHECK(type == content::NOTIFICATION_RENDERER_PROCESS_CREATED);
   content::RenderProcessHost* process =
       content::Source<content::RenderProcessHost>(source).ptr();
   InitForRenderer(process);
@@ skipping 105 matching lines @@
 }
 
 void SpellcheckService::UpdateFeedbackSenderState() {
   if (SpellingServiceClient::IsAvailable(
           context_, SpellingServiceClient::SPELLCHECK)) {
     feedback_sender_->StartFeedbackCollection();
   } else {
     feedback_sender_->StopFeedbackCollection();
   }
 }