Return const by ref instead of value

chrome/browser/ui/ash/system_tray_delegate_chromeos.h

 // Copyright 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.
 
 #ifndef CHROME_BROWSER_UI_ASH_SYSTEM_TRAY_DELEGATE_CHROMEOS_H_
 #define CHROME_BROWSER_UI_ASH_SYSTEM_TRAY_DELEGATE_CHROMEOS_H_
 
 #include <string>
 #include <vector>
 
@@ skipping 61 matching lines @@
 
   void InitializeOnAdapterReady(
       scoped_refptr<device::BluetoothAdapter> adapter);
 
   // Overridden from ash::SystemTrayDelegate:
   void Initialize() override;
   void Shutdown() override;
   bool GetTrayVisibilityOnStartup() override;
   ash::user::LoginStatus GetUserLoginStatus() const override;
   void ChangeProfilePicture() override;
-  const std::string GetEnterpriseDomain() const override;
+  const std::string& GetEnterpriseDomain() const override;

[stevenjb, 2015/09/09 18:10:45]

This shouldn't compile. GetEnterpriseDomain() is is a virtual method that
returns a string. In general, virtual methods shouldn't return references since
a particular implementation might e.g. return a new empty string.

If we actually care about cleaning this up, we should replace 'const string' for
all of these with just 'string' in the ash::SystemTrayDelegate header and all
derived methods.

   const base::string16 GetEnterpriseMessage() const override;
   const std::string GetSupervisedUserManager() const override;
   const base::string16 GetSupervisedUserManagerName() const override;
   const base::string16 GetSupervisedUserMessage() const override;
   bool IsUserSupervised() const override;
   bool IsUserChild() const override;
   void GetSystemUpdateInfo(ash::UpdateInfo* info) const override;
   base::HourClockType GetHourClockType() const override;
   void ShowSettings() override;
   bool ShouldShowSettings() override;
@@ skipping 222 matching lines @@
 
   base::WeakPtrFactory<SystemTrayDelegateChromeOS> weak_ptr_factory_;
 
   DISALLOW_COPY_AND_ASSIGN(SystemTrayDelegateChromeOS);
 };
 
 ash::SystemTrayDelegate* CreateSystemTrayDelegate();
 
 }  // namespace chromeos
 #endif  // CHROME_BROWSER_UI_ASH_SYSTEM_TRAY_DELEGATE_CHROMEOS_H_