Introduce NavigationSimulator to use in unit tests

content/public/test/navigation_simulator.cc

+// Copyright 2017 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 "content/public/test/navigation_simulator.h"
+
+#include "base/memory/ptr_util.h"
+#include "content/public/browser/render_frame_host.h"
+#include "content/test/navigation_simulator_impl.h"
+#include "content/test/test_render_frame_host.h"
+
+namespace content {
+
+// static
+std::unique_ptr<NavigationSimulator>
+NavigationSimulator::CreateRendererInitiated(
+    const GURL& original_url,
+    RenderFrameHost* render_frame_host) {
+  return base::MakeUnique<NavigationSimulatorImpl>(
+      original_url, static_cast<TestRenderFrameHost*>(render_frame_host));
+}
+
+NavigationSimulator::~NavigationSimulator() {}
+
+}  // namespace content