Refactor web shell integration tests utilities.

ios/web/public/test/navigation_test_util.h

+// 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.
+
+#ifndef IOS_WEB_SHELL_PUBLIC_TEST_NAVIGATION_TEST_UTIL_H_
+#define IOS_WEB_SHELL_PUBLIC_TEST_NAVIGATION_TEST_UTIL_H_
+
+#import "ios/web/public/web_state/web_state.h"
+#include "url/gurl.h"
+
+namespace web {
+namespace navigation_test_util {
+
+// Loads |url| in |web_state| with transition of type ui::PAGE_TRANSITION_TYPED.
+void LoadUrl(web::WebState* web_state, const GURL& url);
+
+}  // namespace navigation_test_util
+}  // namespace web
+
+#endif  // IOS_WEB_SHELL_PUBLIC_TEST_NAVIGATION_TEST_UTIL_H_