Remove const qualifier from function return type

components/copresence/public/copresence_delegate.h

 // Copyright 2014 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 COMPONENTS_COPRESENCE_PUBLIC_COPRESENCE_DELEGATE_H_
 #define COMPONENTS_COPRESENCE_PUBLIC_COPRESENCE_DELEGATE_H_
 
 #include <string>
 #include <vector>
 
@@ skipping 30 matching lines @@
   virtual void HandleMessages(
       const std::string& app_id,
       const std::string& subscription_id,
       const std::vector<Message>& messages) = 0;
 
   virtual void HandleStatusUpdate(CopresenceStatus status) = 0;
 
   // Thw URLRequestContextGetter must outlive the CopresenceManager.
   virtual net::URLRequestContextGetter* GetRequestContext() const = 0;
 
-  virtual const std::string GetPlatformVersionString() const = 0;
+  virtual std::string GetPlatformVersionString() const = 0;
 
-  virtual const std::string GetAPIKey(const std::string& app_id) const = 0;
+  virtual std::string GetAPIKey(const std::string& app_id) const = 0;
 
   // The WhispernetClient must outlive the CopresenceManager.
   virtual audio_modem::WhispernetClient* GetWhispernetClient() = 0;
 
   // Clients may optionally provide a GCMDriver to receive messages from.
   // If no driver is available, this can return null.
   virtual gcm::GCMDriver* GetGCMDriver() = 0;
 
   // Get the copresence device ID for authenticated or anonymous calls,
   // as specified. If none exists, return the empty string.
-  virtual const std::string GetDeviceId(bool authenticated) = 0;
+  virtual std::string GetDeviceId(bool authenticated) = 0;
 
   // Save a copresence device ID for authenticated or anonymous calls.
   // If the device ID is empty, any stored ID should be deleted.
   virtual void SaveDeviceId(bool authenticated,
                             const std::string& device_id) = 0;
 
  protected:
   virtual ~CopresenceDelegate() {}
 };
 
 }  // namespace copresence
 
 #endif  // COMPONENTS_COPRESENCE_PUBLIC_COPRESENCE_DELEGATE_H_