Add VrShell feature flag and wire it up to VrShell delegate.

content/public/common/content_features.cc

 // 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.
 
 #include "build/build_config.h"
 #include "content/public/common/content_features.h"
 
 namespace features {
 
 // All features in alphabetical order.
@@ skipping 214 matching lines @@
 
 // Use IME's own thread instead of using main UI thread. It also means that
 // we will not use replica editor and do a round trip to renderer to synchronize
 // with Blink data.
 const base::Feature kImeThread{"ImeThread", base::FEATURE_ENABLED_BY_DEFAULT};
 
 // FeatureList definition for the Seccomp field trial.
 const base::Feature kSeccompSandboxAndroid{"SeccompSandboxAndroid",
                                            base::FEATURE_DISABLED_BY_DEFAULT};
 
+// Enables VR UI.
+const base::Feature kVrShell{"VrShell", base::FEATURE_DISABLED_BY_DEFAULT};
+
 // The JavaScript API for payments on the web.
 const base::Feature kWebPayments{"WebPayments",
                                  base::FEATURE_ENABLED_BY_DEFAULT};
 
 #endif
 
 #if defined(OS_WIN)
 // Emergency "off switch" for new Windows sandbox security mitigation,
 // sandbox::MITIGATION_EXTENSION_POINT_DISABLE.
 const base::Feature kWinSboxDisableExtensionPoints{
     "WinSboxDisableExtensionPoint", base::FEATURE_ENABLED_BY_DEFAULT};
 #endif
 
 }  // namespace features