Add chrome://vr-shell-ui internal page

chrome/common/features.gni

 # Copyright 2015 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.
 
 # This is the GN version of //chrome/chrome_features.gypi.
 # Please keep in sync!
 
 import("//build/config/chrome_build.gni")
 import("//build/config/chromecast_build.gni")
 import("//build/config/compiler/compiler.gni")
@@ skipping 21 matching lines @@
   # ChromeOS builds have this enabled by default.
   enable_hotwording = is_chrome_branded && is_chromeos
 
   # Set to true to bundle all the mash related mojo services into chrome.
   # Specify --mash to chrome to have chrome start the mash environment.
   enable_package_mash_services = is_chromeos
 
   # Enables vr shell.
   enable_vr_shell = false
 
+  # Enables vr shell UI development on local or remote page.
+  enable_vr_shell_ui_dev = false
+
   # Enable native notifications via XPC services (mac only).
   enable_xpc_notifications = false
 
   # Use vulcanized HTML/CSS/JS resources to speed up WebUI (chrome://)
   # pages. https://github.com/polymer/vulcanize
   use_vulcanize = true
 
   # Indicates if the build is using PGO.
   pgo_build = chrome_pgo_phase > 0
 }
 
 chrome_grit_defines = [
   "enable_background=$enable_background",
   "enable_google_now=$enable_google_now",
   "enable_hotwording=$enable_hotwording",
+  "enable_vr_shell=$enable_vr_shell",
   "use_vulcanize=$use_vulcanize",
 ]