Created NavigationManager::CopyStateFromAndPrune().

ios/web/navigation/navigation_manager_impl.mm

Index: ios/web/navigation/navigation_manager_impl.mm
diff --git a/ios/web/navigation/navigation_manager_impl.mm b/ios/web/navigation/navigation_manager_impl.mm
index 572bb30365d27963d17a2d17b2d4931f461796ae..f609eb2f97ea0dbbec8bab39a7e73bba5e38adfc 100644
--- a/ios/web/navigation/navigation_manager_impl.mm
+++ b/ios/web/navigation/navigation_manager_impl.mm
@@ -358,6 +358,14 @@ bool AreURLsInPageNavigation(const GURL& existing_url, const GURL& new_url) {
   delegate_->GetWebState()->OpenURL(params);
 }
 
+void NavigationManagerImpl::InsertStateFromManager(
+    const NavigationManager* manager) {
+  DCHECK(manager);
+  CRWSessionController* other_session =
+      static_cast<const NavigationManagerImpl*>(manager)->session_controller_;
+  [session_controller_ insertStateFromSessionController:other_session];
+}
+
 std::unique_ptr<std::vector<BrowserURLRewriter::URLRewriter>>
 NavigationManagerImpl::GetTransientURLRewriters() {
   return std::move(transient_url_rewriters_);