Adds button to VRShell menu mode, which lets the user manually exit WebVR presentation.

chrome/browser/ui/webui/vr_shell/vr_shell_ui_ui.cc

 // 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 "chrome/browser/ui/webui/vr_shell/vr_shell_ui_ui.h"
 
 #include <string>
 #include <unordered_set>
 
 #include "base/memory/ptr_util.h"
@@ skipping 183 matching lines @@
   source->AddResourcePath("vk.css", IDR_VR_SHELL_UI_VK_CSS);
   source->AddResourcePath("vk.js", IDR_VR_SHELL_UI_VK_JS);
   source->SetDefaultResource(IDR_VR_SHELL_UI_HTML);
   source->AddLocalizedString("insecureWebVrContentPermanent",
                              IDS_PAGE_INFO_INSECURE_WEBVR_CONTENT_PERMANENT);
   source->AddLocalizedString("insecureWebVrContentTransient",
                              IDS_PAGE_INFO_INSECURE_WEBVR_CONTENT_TRANSIENT);
   source->AddLocalizedString("back", IDS_VR_SHELL_UI_BACK_BUTTON);
   source->AddLocalizedString("forward", IDS_VR_SHELL_UI_FORWARD_BUTTON);
   source->AddLocalizedString("reload", IDS_VR_SHELL_UI_RELOAD_BUTTON);
+  source->AddLocalizedString("exitPresent",
+                             IDS_VR_SHELL_UI_EXIT_PRESENT_BUTTON);
   source->AddLocalizedString("newTab", IDS_VR_SHELL_NEW_TAB_BUTTON);
   source->AddLocalizedString("newIncognitoTab",
                              IDS_VR_SHELL_NEW_INCOGNITO_TAB_BUTTON);
 
   return source;
 }
 #endif
 
 }  // namespace
 
 VrShellUIUI::VrShellUIUI(content::WebUI* web_ui) : WebUIController(web_ui) {
   Profile* profile = Profile::FromWebUI(web_ui);
 #if !defined(ENABLE_VR_SHELL_UI_DEV)
   content::WebUIDataSource::Add(profile, CreateVrShellUIHTMLSource());
 #else
   content::URLDataSource::Add(
       profile, new RemoteDataSource(profile->GetRequestContext()));
 #endif
   web_ui->AddMessageHandler(base::MakeUnique<VrShellUIMessageHandler>());
 }
 
 VrShellUIUI::~VrShellUIUI() {}