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

chrome/browser/extensions/extension_browsertest.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/extensions/extension_browsertest.h"
 
 #include <vector>
 
 #include "base/command_line.h"
 #include "base/files/file_path.h"
@@ skipping 551 matching lines @@
       VLOG(1) << *iter;
 
     return NULL;
   }
 
   if (!observer_->WaitForExtensionViewsToLoad())
     return NULL;
   return service->GetExtensionById(last_loaded_extension_id(), false);
 }
 
-void ExtensionBrowserTest::ReloadExtension(const std::string extension_id) {
+void ExtensionBrowserTest::ReloadExtension(const std::string& extension_id) {
   observer_->Watch(extensions::NOTIFICATION_EXTENSION_LOADED_DEPRECATED,
                    content::NotificationService::AllSources());
 
   ExtensionService* service =
       extensions::ExtensionSystem::Get(profile())->extension_service();
   service->ReloadExtension(extension_id);
 
   observer_->Wait();
   observer_->WaitForExtensionViewsToLoad();
 }
@@ skipping 99 matching lines @@
   return extensions::browsertest_util::ExecuteScriptInBackgroundPage(
       profile(), extension_id, script);
 }
 
 bool ExtensionBrowserTest::ExecuteScriptInBackgroundPageNoWait(
     const std::string& extension_id,
     const std::string& script) {
   return extensions::browsertest_util::ExecuteScriptInBackgroundPageNoWait(
       profile(), extension_id, script);
 }