Add GetCurrentNativeController to webstate.

ios/web/public/test/native_controller_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.
+
+#import "ios/web/public/test/native_controller_test_util.h"
+
+#import "ios/web/web_state/ui/crw_web_controller.h"
+#import "ios/web/web_state/web_state_impl.h"
+
+namespace web {
+namespace test {
+
+id GetCurrentNativeController(WebState* web_state) {
+  web::WebStateImpl* web_state_impl =
+      static_cast<web::WebStateImpl*>(web_state);
+  return [web_state_impl->GetWebController() nativeController];
+}
+
+}  // namespace test
+}  // namespace web