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

chrome/browser/ui/webui/ntp/new_tab_page_sync_handler_browsertest.cc

 // Copyright (c) 2013 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/ui/webui/ntp/new_tab_page_sync_handler.h"
 
 #include "base/prefs/pref_service.h"
 #include "chrome/browser/ui/browser.h"
 #include "chrome/browser/ui/tabs/tab_strip_model.h"
 #include "chrome/common/pref_names.h"
 #include "chrome/common/url_constants.h"
 #include "chrome/test/base/in_process_browser_test.h"
 #include "chrome/test/base/testing_profile.h"
 #include "chrome/test/base/ui_test_utils.h"
 #include "content/public/browser/web_contents.h"
 #include "content/public/browser/web_ui.h"
 #include "content/public/test/browser_test_utils.h"
 #include "testing/gmock/include/gmock/gmock.h"
 #include "url/gurl.h"
 
 using ::testing::_;
 
 typedef InProcessBrowserTest NewTabPageSyncHandlerBrowserTest;
 
 class MockNewTabPageSyncHandler : public NewTabPageSyncHandler {
  public:
-  MOCK_METHOD3(SendSyncMessageToPage, void(MessageType type, std::string msg,
-      std::string linktext));
+  MOCK_METHOD3(SendSyncMessageToPage,
+               void(MessageType type,
+                    const std::string& msg,
+                    const std::string& linktext));
 
   void SetWaitingForInitialPageLoad(bool waiting) {
     waiting_for_initial_page_load_ = waiting;
   }
 };
 
 // TODO(samarth): Delete along with the rest of the NTP4 code.
 IN_PROC_BROWSER_TEST_F(NewTabPageSyncHandlerBrowserTest,
                        DISABLED_ChangeSigninAllowedToFalse) {
   ui_test_utils::NavigateToURL(browser(), GURL(chrome::kChromeUINewTabURL));
   content::WebUI* web_ui =
       browser()->tab_strip_model()->GetActiveWebContents()->GetWebUI();
   MockNewTabPageSyncHandler* mock_handler = new MockNewTabPageSyncHandler();
   mock_handler->SetWaitingForInitialPageLoad(false);
   web_ui->AddMessageHandler(mock_handler);
   EXPECT_CALL(*mock_handler, SendSyncMessageToPage(mock_handler->HIDE, _, _));
   browser()->profile()->GetPrefs()->SetBoolean(prefs::kSigninAllowed, false);
 }