Refactor web shell integration tests utilities.

ios/web/public/test/navigation_test_util.mm

+// Copyright 2016 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.
+
+#include "ios/web/public/test/navigation_test_util.h"
+
+#import "ios/web/public/navigation_manager.h"
+
+using web::NavigationManager;
+
+namespace web {
+namespace navigation_test_util {
+
+void LoadUrl(web::WebState* web_state, const GURL& url) {
+  NavigationManager* navigation_manager = web_state->GetNavigationManager();
+  NavigationManager::WebLoadParams params(url);
+  params.transition_type = ui::PAGE_TRANSITION_TYPED;
+  navigation_manager->LoadURLWithParams(params);
+}
+
+}  // namespace navigation_test_util
+}  // namespace web