Created NavigationManager::CopyStateFromAndPrune().

ios/web/public/navigation_manager.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 IOS_WEB_PUBLIC_NAVIGATION_MANAGER_H_
 #define IOS_WEB_PUBLIC_NAVIGATION_MANAGER_H_
 
 #include <stddef.h>
 
 #import "base/mac/scoped_nsobject.h"
@@ skipping 143 matching lines @@
   // or follows the current index.
   virtual NavigationItemList GetBackwardItems() const = 0;
   virtual NavigationItemList GetForwardItems() const = 0;
 
   // Reloads the current item. If |check_for_repost| is true and the current
   // item has POST data the user is prompted to see if they really want to
   // reload the page. In nearly all cases pass in true.  If a transient item is
   // showing, initiates a new navigation to its URL.
   virtual void Reload(bool check_for_repost) = 0;
 
+  // Inserts copies of |other_controller|'s NavigationItems to the front of this
+  // session history.
+  virtual void InsertStateFromManager(const NavigationManager* manager) = 0;

[Eugene But (OOO till 7-30), 2017/03/11 00:27:47]

Per my previous comments can we mirror content? Maybe CopyStateFromAndPrune is
the right API?

+
   // Forces the pending item to be loaded using desktop user agent. Note that
   // the pending item may or may not already exist.
   // TODO(crbug.com/692303): Remove this when overriding the user agent doesn't
   // create a new NavigationItem.
   virtual void OverrideDesktopUserAgentForNextPendingItem() = 0;
 };
 
 }  // namespace web
 
 #endif  // IOS_WEB_PUBLIC_NAVIGATION_MANAGER_H_