Remove migration of obsolete value for "session.restore_on_startup".

chrome/browser/sessions/restore_on_startup_policy_handler.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_SESSIONS_RESTORE_ON_STARTUP_POLICY_HANDLER_H_
 #define CHROME_BROWSER_SESSIONS_RESTORE_ON_STARTUP_POLICY_HANDLER_H_
 
 #include "components/policy/core/browser/configuration_policy_handler.h"
 
 class PrefValueMap;
 
 namespace policy {
 
 class PolicyErrorMap;
 class PolicyMap;
 
 // Handles RestoreOnStartup policy.
 class RestoreOnStartupPolicyHandler : public TypeCheckingPolicyHandler {
  public:
   RestoreOnStartupPolicyHandler();
   ~RestoreOnStartupPolicyHandler() override;
 
   // ConfigurationPolicyHandler methods:
   bool CheckPolicySettings(const PolicyMap& policies,
                            PolicyErrorMap* errors) override;
   void ApplyPolicySettings(const PolicyMap& policies,
                            PrefValueMap* prefs) override;
 
  private:
-  void ApplyPolicySettingsFromHomePage(const PolicyMap& policies,
-                                       PrefValueMap* prefs);
-
   DISALLOW_COPY_AND_ASSIGN(RestoreOnStartupPolicyHandler);
 };
 
 }  // namespace policy
 
 #endif  // CHROME_BROWSER_SESSIONS_RESTORE_ON_STARTUP_POLICY_HANDLER_H_