Refactor serialisation of openerId & openerNavigationIndex.

ios/web/public/crw_session_storage.h

 // Copyright 2015 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 IOS_WEB_PUBLIC_CRW_SESSION_STORAGE_H_
 #define IOS_WEB_PUBLIC_CRW_SESSION_STORAGE_H_
 
 #import <Foundation/Foundation.h>
 #include <memory>
 
 @class CRWSessionCertificatePolicyManager;
 
 namespace web {
 class SerializableUserData;
 }
 
 // NSCoding-compliant class used to serialize session state.
 // TODO(crbug.com/685388): Investigate using code from the sessions component.
 @interface CRWSessionStorage : NSObject<NSCoding>
 
-@property(nonatomic, copy) NSString* openerID;
 @property(nonatomic, getter=isOpenedByDOM) BOOL openedByDOM;
-@property(nonatomic, assign) NSInteger openerNavigationIndex;
 @property(nonatomic, copy) NSString* windowName;
 @property(nonatomic, assign) NSInteger currentNavigationIndex;
 @property(nonatomic, assign) NSInteger previousNavigationIndex;
 @property(nonatomic, assign) NSTimeInterval lastVisitedTimestamp;
 @property(nonatomic, copy) NSArray* itemStorages;
 @property(nonatomic, retain)
     CRWSessionCertificatePolicyManager* sessionCertificatePolicyManager;
 @property(nonatomic, readonly) web::SerializableUserData* userData;
 
 // Setter for |userData|.  The receiver takes ownership of |userData|.
 - (void)setSerializableUserData:
     (std::unique_ptr<web::SerializableUserData>)userData;
 
 @end
 
 #endif  // IOS_WEB_PUBLIC_CRW_SESSION_STORAGE_H_