Jonas Jenwald 472bbf4592 Unblock the "load" event in inactive windows/tabs (bug 1746213, PR 11646 follow-up)
Given that `requestAnimationFrame` is being used, see the `src/diplay/api.js` file, an inactive window/tab means that rendering will not run and we'll thus not fetch all pages. The latter is a requirement for the "load" event to be unblocked, in the MOZCENTRAL-version of, the default viewer.

This patch is a *partial* solution, since it only addresses the following situations:
 - A *background*  tab (containing the viewer) is reloaded, e.g. via the tab-bar context menu.
 - The viewer is loaded in a active tab, but the user switches away from it (or switches to another program window) *before* rendering has started.
2021-12-19 10:39:48 +01:00
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