1800914 - Don't suspend event pages until the browser has fully started up

Status: NEW

(WebExtensions :: General, enhancement, P3)

Description

[Rob Wu [:robwu]]

Event pages are currently suspended after some period of inactivity. One of the triggers is event dispatch. We reset the timer here at the start of fire in EventManager: https://searchfox.org/mozilla-central/rev/219df29d0fb5d8928ae41bba4a605046de411cf0/toolkit/components/extensions/ExtensionCommon.jsm#2500-2507,2513,2522,2533,2541. The assumption here is that the event handler should complete within that time.

Firefox can be slow at startup, outside the control of extensions, and consequently that assumption may be incorrect. To cater for that, we should use a more dynamic approach to suspending pages, e.g. not suspending pages shortly after browser startup. At least for known cases where extension APIs are knowingly not responding soon enough (e.g. bug 1741865, specifically the runtime.onStartup event as mentioned in https://bugzilla.mozilla.org/show_bug.cgi?id=1741865#c60).