* Refactor shouldUpdateScroll passing
So far, shouldUpdateScroll has been manually passed down from the very top of
the React component hierarchy even though it is a static function common to
all ScrollContainer instances, so replaced that with a custom class extending
ScrollContainer.
* Generalize “press back to close modal” to any modal and to public pages
* Fix boost confirmation modal closing media modal
- Change overlay background to match color of viewed image
- Add interactive reply/boost/favourite buttons to footer of modal
- Change ugly "View context" link to button among the action bar
* Fix lost focus after modal closes
Regression caused by the use of the wicg-inert polyfill
* Fix regression introduced by wicg-inert
* Catch errors to please CodeClimate
The modal-handling code gives back focus to the element focused when the
modal opened. However, in the case of reply confirmation, it would do so
*after* the composer code itself requested focus.
