Only commit cookie changes in prerenders after a prerender is shown

net/cookies/canonical_cookie.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.
 
 #ifndef NET_COOKIES_CANONICAL_COOKIE_H_
 #define NET_COOKIES_CANONICAL_COOKIE_H_
 
 #include <string>
 #include <vector>
 
@@ skipping 107 matching lines @@
 
   // Returns true if the cookie should be included for the given request |url|.
   // HTTP only cookies can be filter by using appropriate cookie |options|.
   // PLEASE NOTE that this method does not check whether a cookie is expired or
   // not!
   bool IncludeForRequestURL(const GURL& url,
                             const CookieOptions& options) const;
 
   std::string DebugString() const;
 
+  // Returns a duplicate of this cookie.
+  CanonicalCookie* Duplicate();
+
   // Returns the cookie source when cookies are set for |url|. This function
   // is public for unit test purposes only.
   static std::string GetCookieSourceFromURL(const GURL& url);
   static std::string CanonPath(const GURL& url, const ParsedCookie& pc);
   static base::Time CanonExpiration(const ParsedCookie& pc,
                                     const base::Time& current,
                                     const base::Time& server_time);
 
  private:
+  // NOTE: When any new members are added below, the implementation of
+  // Duplicate() must be updated to copy the new member accordingly.
+
   // The source member of a canonical cookie is the origin of the URL that tried
   // to set this cookie, minus the port number if any.  This field is not
   // persistent though; its only used in the in-tab cookies dialog to show the
   // user the source URL. This is used for both allowed and blocked cookies.
   // When a CanonicalCookie is constructed from the backing store (common case)
   // this field will be null.  CanonicalCookie consumers should not rely on
   // this field unless they guarantee that the creator of those
   // CanonicalCookies properly initialized the field.
   std::string source_;
   std::string name_;
   std::string value_;
   std::string domain_;
   std::string path_;
   base::Time creation_date_;
   base::Time expiry_date_;
   base::Time last_access_date_;
   bool secure_;
   bool httponly_;
   CookiePriority priority_;
+  // NOTE: When any new members are added above this comment, the
+  // implementation of Duplicate() must be updated to copy the new member
+  // accordingly.
 };
 
 typedef std::vector<CanonicalCookie> CookieList;
 
 }  // namespace net
 
 #endif  // NET_COOKIES_CANONICAL_COOKIE_H_