Stay in VR while showing DOFF flow and connect CCT exit button to this.

chrome/browser/android/vr_shell/ui_scene_manager.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 "chrome/browser/android/vr_shell/ui_scene_manager.h"
 
 #include "base/callback.h"
 #include "base/memory/ptr_util.h"
 #include "chrome/browser/android/vr_shell/textures/close_button_texture.h"
 #include "chrome/browser/android/vr_shell/textures/ui_texture.h"
@@ skipping 397 matching lines @@
 void UiSceneManager::SetIsExiting() {
   if (scene_->is_exiting())
     return;
   scene_->set_is_exiting();
   ConfigureScene();
 }
 
 void UiSceneManager::SetHistoryButtonsEnabled(bool can_go_back,
                                               bool can_go_forward) {}
 
-void UiSceneManager::OnCloseButtonClicked() {}
+void UiSceneManager::OnCloseButtonClicked() {
+  browser_->ExitCct();
+}
 
 int UiSceneManager::AllocateId() {
   return next_available_id_++;
 }
 
 }  // namespace vr_shell