1816470 - Add check to ensure detectOnly Mode not enabled in dangling state

Status: NEW

(Core :: Privacy: Anti-Tracking, enhancement)

Description

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Mimic Android implementation to ensure detectOnly mode disabled by default unless enable conditions met on browser start. (Implementation for ref: https://github.com/mozilla-mobile/fenix/pull/28824 )

-By default detectOnly mode is disabled

1. Browser determines if detectOnly mode to be enabled by checking if CBH enabled preference set or timeout has passed
2. When enabled will prompt user to opt-in to CBH on first appearance of banner
3. detectOnly detects banner and begins onboarding flow
   a) user communicates a preference (opt-in or opt-out of CBH) and detectOnly is disabled from now on
   b) user exits off onboarding prompt without communicating opt-in/opt-out. detectOnly is disabled for 8 hours and then re-enabled to prompt the user again

Background: There us concern detectOnly mode could be left enabled even after a user expresses a preference for whether they want CBH enabled or not. This could lead to potential performance hits as the code continues to run needlessly in the background.