[vr] Exit VR mode when we encounter unsupported URLs

chrome/browser/android/vr_shell/ui_unsupported_mode.h

 // 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.
 
 #ifndef CHROME_BROWSER_ANDROID_VR_SHELL_UI_UNSUPPORTED_MODE_H_
 #define CHROME_BROWSER_ANDROID_VR_SHELL_UI_UNSUPPORTED_MODE_H_
 
 namespace vr_shell {
 
 // Ensure that this stays in sync with VRUnsupportedMode in enums.xml
 // These values are written to logs.  New enum values can be added, but existing
 // enums must never be renumbered or deleted and reused.
 enum class UiUnsupportedMode : int {
   kUnhandledCodePoint = 0,
+  kCouldNotElideURL,
 
   // This must be last.
   kCount,
 };
 
 }  // namespace vr_shell
 
 #endif  // CHROME_BROWSER_ANDROID_VR_SHELL_UI_UNSUPPORTED_MODE_H_