Replacing const by value return values into const by ref in chrome/browser/extensions/api/identity

chrome/browser/extensions/api/identity/identity_apitest.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 <set>
 #include <string>
 #include <vector>
 
 #include "base/command_line.h"
 #include "base/prefs/pref_service.h"
@@ skipping 706 matching lines @@
     extension_id_ = ext->id();
     oauth_scopes_ = std::set<std::string>(oauth2_info.scopes.begin(),
                                           oauth2_info.scopes.end());
     return ext;
   }
 
   IdentityAPI* id_api() {
     return IdentityAPI::GetFactoryInstance()->Get(browser()->profile());
   }
 
-  const std::string GetPrimaryAccountId() {
+  const std::string& GetPrimaryAccountId() {
     SigninManagerBase* signin_manager =
         SigninManagerFactory::GetForProfile(browser()->profile());
     return signin_manager->GetAuthenticatedAccountId();
   }
 
   void SetCachedToken(const IdentityTokenCacheValue& token_data) {
     ExtensionTokenKey key(extension_id_, GetPrimaryAccountId(), oauth_scopes_);
     id_api()->SetCachedToken(key, token_data);
   }
 
@@ skipping 1087 matching lines @@
   EXPECT_EQ(std::string("https://abcdefghij.chromiumapp.org/callback#test"),
             url);
 }
 
 }  // namespace extensions
 
 // Tests the chrome.identity API implemented by custom JS bindings .
 IN_PROC_BROWSER_TEST_F(ExtensionApiTest, ChromeIdentityJsBindings) {
   ASSERT_TRUE(RunExtensionTest("identity/js_bindings")) << message_;
 }