Remove the force_session cookie option, as it's not used anymore

net/cookies/cookie_options.h

 // 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.
 
 // Brought to you by number 42.
 
 #ifndef NET_COOKIES_COOKIE_OPTIONS_H_
 #define NET_COOKIES_COOKIE_OPTIONS_H_
 #pragma once
 
 namespace net {
 
 class CookieOptions {
  public:
   // Default is to exclude httponly, which means:
   // - reading operations will not return httponly cookies.
   // - writing operations will not write httponly cookies.
   CookieOptions()
-      : exclude_httponly_(true),
-        force_session_(false) {
+      : exclude_httponly_(true) {
   }
 
   void set_exclude_httponly() { exclude_httponly_ = true; }
   void set_include_httponly() { exclude_httponly_ = false; }
   bool exclude_httponly() const { return exclude_httponly_; }
 
-  // Forces a cookie to be saved as a session cookie. If the expiration time of
-  // the cookie is in the past, i.e. the cookie would end up being deleted, this
-  // option is ignored. See CookieMonsterTest.ForceSessionOnly.
-  void set_force_session() { force_session_ = true; }
-  bool force_session() const { return force_session_; }
-
  private:
   bool exclude_httponly_;
-  bool force_session_;
 };
 }  // namespace net
 
 #endif  // NET_COOKIES_COOKIE_OPTIONS_H_