Created NavigationManager::CopyStateFromAndPrune().

ios/chrome/browser/ui/browser_view_controller.mm

Index: ios/chrome/browser/ui/browser_view_controller.mm
diff --git a/ios/chrome/browser/ui/browser_view_controller.mm b/ios/chrome/browser/ui/browser_view_controller.mm
index 6a4a6377932b8bb80bc74322b25a863d130bcf91..9d1a6bfb421b1fd72832044152a7b607ab025501 100644
--- a/ios/chrome/browser/ui/browser_view_controller.mm
+++ b/ios/chrome/browser/ui/browser_view_controller.mm
@@ -3678,15 +3678,15 @@ - (void)loadURL:(const GURL&)url
     Tab* newTab = [_preloadController releasePrerenderContents];
     DCHECK(oldTab);
     DCHECK(newTab);
-    if (oldTab && newTab) {
+    BOOL canPruneItems =

[Eugene But (OOO till 7-30), 2017/03/15 19:54:51]

s/BOOL/bool

[kkhorimoto, 2017/03/15 21:04:38]

Done.

+        [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];