1844486 - BackgroundWorker build and shutdown should gracefully handle early interruption

Status: NEW

(WebExtensions :: General, defect, P3)

Description

[Rob Wu [:robwu]]

The current build/shutdown logic of the background service worker seems to rely on the assumption that shutdown is only called once build has finished. The code doesn't account for early interruptions, which can potentially cause the BackgroundWorker's logic to be stuck waiting for a notification that never arrives:

• build waiting for context, potentially forever: https://searchfox.org/mozilla-central/rev/4537bb2abc8eb49506bbad27b89ab364ac3062d3/toolkit/components/extensions/parent/ext-backgroundPage.js#180-184,187
• build with multiple await + shutdown that can't interrupt early: https://searchfox.org/mozilla-central/rev/4537bb2abc8eb49506bbad27b89ab364ac3062d3/toolkit/components/extensions/parent/ext-backgroundPage.js#194,198-201 .

For comparison, the BackgroundPage implementation does guarantee that shutdown() can be called at any point, and that the result is eventually cleaned up. This is relies upon to support atomic backgroundState transitions in bug 1762225.