* Rename toolkit's add.svg to plus.svg, use it for the zoom-in buttons and about:newtab's add icon Differential Revision: https://phabricator.services.mozilla.com/D118627
* Rename toolkit's add.svg to plus.svg, use it for the zoom-in buttons and about:newtab's add icon Differential Revision: https://phabricator.services.mozilla.com/D118627