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/. */

 /*

 Listen for left and right click events and send the corresponding message

 to the content script.

 */

 this.addEventListener('click', function(event) {

   if(event.button == 0 && event.shiftKey == false)

     self.port.emit('left-click');

   if(event.button == 2 || (event.button == 0 && event.shiftKey == true))

     self.port.emit('right-click');

     event.preventDefault();

 }, true);