Created NavigationManager::CopyStateFromAndPrune().

ios/chrome/browser/ui/browser_view_controller.mm

 // Copyright 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.
 
 #import "ios/chrome/browser/ui/browser_view_controller.h"
 
 #import <AssetsLibrary/AssetsLibrary.h>
 #import <MobileCoreServices/MobileCoreServices.h>
 #import <PassKit/PassKit.h>
 #import <Photos/Photos.h>
@@ skipping 3660 matching lines @@
     // In debug the app can continue working even after the CHECK. Adding a
     // return avoids the crash url to be added to the history.
     return;
   }
 
   if (url == [_preloadController prerenderedURL]) {
     Tab* oldTab = [_model currentTab];
     Tab* newTab = [_preloadController releasePrerenderContents];
     DCHECK(oldTab);
     DCHECK(newTab);
-    if (oldTab && newTab) {
+    BOOL canPruneItems =
+        [newTab navigationManager]->CanPruneAllButLastCommittedItem();
+    if (oldTab && newTab && canPruneItems) {
       [oldTab recordStateInHistory];
-      DCHECK([newTab navigationManager]);
       CRWSessionController* newHistory =
           [newTab navigationManagerImpl]->GetSessionController();
-      DCHECK([oldTab navigationManager]);
       CRWSessionController* oldHistory =
           [oldTab navigationManagerImpl]->GetSessionController();
-      [newHistory insertStateFromSessionController:oldHistory];
+      [newHistory copyStateFromSessionControllerAndPrune:oldHistory];
       [[newTab nativeAppNavigationController]
           copyStateFrom:[oldTab nativeAppNavigationController]];
       [_model replaceTab:oldTab withTab:newTab];
 
       // Set isPrerenderTab to NO after replacing the tab. This will allow the
       // BrowserViewController to detect that a pre-rendered tab is switched in,
       // and show the prerendering animation.
       newTab.isPrerenderTab = NO;
 
       [self tabLoadComplete:newTab withSuccess:newTab.loadFinished];
@@ skipping 1429 matching lines @@
 
 - (UIView*)voiceSearchButton {
   return _voiceSearchButton;
 }
 
 - (id<LogoAnimationControllerOwner>)logoAnimationControllerOwner {
   return [self currentLogoAnimationControllerOwner];
 }
 
 @end