The Tor Browser / file revision

 /* This Source Code Form is subject to the terms of the Mozilla Public

  * License, v. 2.0. If a copy of the MPL was not distributed with this

  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */

 /**

  * Optimization for tabs that are restored lazily. We can save a good amount of

  * memory that to-be-restored tabs would otherwise consume simply by setting

  * their browsers to 'display: none' as that will prevent them from having to

  * create a presentation and the like.

  */

 browser[pending] {

   display: none;

 }