Add-on will always enable itself if doh-rollout.previous.trr.mode doesn't exist

[nhnt11]

The add-on will not respect the value of the enabled pref or the study branch while checking whether to enable itself for new users ("new" in the sense that doh-rollout.previous.trr.mode is unset).

When fetching the value of this pref, we pass 0 as the default value if it doesn't exist [1], and later we check for a 0 value which will evaluate to true [2].

[1] https://github.com/mozilla/doh-rollout/blob/ec651685125bdf566c7ffd791d09aa3703990202/src/background.js#L547

[2] https://github.com/mozilla/doh-rollout/blob/ec651685125bdf566c7ffd791d09aa3703990202/src/background.js#L563

[nhi-nguyen]

This means that the addon will run for users in the control branch.

@mariaberlinger Once this issue is fixed and a new version is available for testing, please verify that the issue is indeed fixed, by checking that the addon doesn't run for users in the control branch.

[mariaberlinger]

@nhi-nguyen we were under the impression that this feature will be Rolled out. In this case, branches are not supported for the current addon-rollout action. Can you please confirm if v1.2 will be a Rollout or a Branched add-on experiment?

[maxxcrawford]

@mariaberlinger @nhi-nguyen v1.2 will be deployed via Normandy as a study/experiement.

There is a separate task of migrating this add-on to Nightly/in-tree, where the actual rollout will happen.