Extract NavigationManagerImpl interface for navigation experiment.

ios/web/web_state/web_state_impl.mm

 // 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.
 
 #import "ios/web/web_state/web_state_impl.h"
 
 #include <stddef.h>
 #include <stdint.h>
 
 #include "base/logging.h"
 #include "base/memory/ptr_util.h"
 #include "base/metrics/histogram_macros.h"
 #include "base/strings/sys_string_conversions.h"
 #import "ios/web/interstitials/web_interstitial_impl.h"
 #import "ios/web/navigation/crw_session_controller.h"
+#import "ios/web/navigation/legacy_navigation_manager_impl.h"
 #import "ios/web/navigation/navigation_item_impl.h"
 #import "ios/web/navigation/session_storage_builder.h"
 #include "ios/web/public/browser_state.h"
 #import "ios/web/public/crw_session_storage.h"
 #import "ios/web/public/java_script_dialog_presenter.h"
 #import "ios/web/public/navigation_item.h"
 #include "ios/web/public/url_util.h"
 #import "ios/web/public/web_client.h"
 #import "ios/web/public/web_state/context_menu_params.h"
 #import "ios/web/public/web_state/ui/crw_content_view.h"
@@ skipping 47 matching lines @@
       is_being_destroyed_(false),
       web_controller_(nil),
       interstitial_(nullptr),
       created_with_opener_(params.created_with_opener),
       weak_factory_(this) {
   // Create or deserialize the NavigationManager.
   if (session_storage) {
     SessionStorageBuilder session_storage_builder;
     session_storage_builder.ExtractSessionState(this, session_storage);
   } else {
-    navigation_manager_ = base::MakeUnique<NavigationManagerImpl>();
+    navigation_manager_ = base::WrapUnique<NavigationManagerImpl>(
+        new LegacyNavigationManagerImpl);
     certificate_policy_cache_ =
         base::MakeUnique<SessionCertificatePolicyCacheImpl>();
   }
   navigation_manager_->SetDelegate(this);
   navigation_manager_->SetBrowserState(params.browser_state);
   // Send creation event and create the web controller.
   GlobalWebStateEventTracker::GetInstance()->OnWebStateCreated(this);
   web_controller_.reset([[CRWWebController alloc] initWithWebState:this]);
 }
 
@@ skipping 615 matching lines @@
     const LoadCommittedDetails& load_details) {
   for (auto& observer : observers_)
     observer.NavigationItemCommitted(load_details);
 }
 
 WebState* WebStateImpl::GetWebState() {
   return this;
 }
 
 }  // namespace web