Firefox: Prepare for non-persistent background page

[gorhill]

Description

Admittedly, I am a bit late at this.

See:

• https://developer.mozilla.org/en-US/docs/Mozilla/Add-ons/WebExtensions/Background_scripts#convert_to_non-persistent
• https://discourse.mozilla.org/t/is-non-persistent-background-script-mandatory-for-android/123839

To do:

• Verify and fix as needed that auxiliary pages are behaving properly when the uBO background page is terminated
• Evaluate how port closing affects content scripts -- this might be the most problematic aspect of being non-persistent
  • This means the generic cosmetic filtering surveyor may be interrupted even though there still could be matching generic cosmetic filters to come
• Optimize timing to generate a selfie, which will be even more key to quickly load back uBO's process into memory
• Evaluate using storage.session to further speed up load sequence

[rtx2080tix]

@gorhill

I don't think that is necessary at all persistent background page is the best because it is very reliable even if it uses more RAM

why would you be interested to implement something that has a lot of disadvantages and drawbacks

[gorhill]

• https://github.com/gorhill/uBlock/commit/5a338b72107f51731bb9dfdae3086eb8c99f3228
• https://github.com/gorhill/uBlock/commit/eb66820728c2275470776550112c60f1741e553f