One question that always comes up with experiments is how they should behave in private browsing mode. Depending on the experiment, we may want it to apply to both PBM and non-PBM, only non-PBM, only PBM, or way may want a different treatment between the two. The doc should call that out somewhere. The doc should also discuss some implementation subtleties. When an extension is loaded temporarily, it doesn't have access to PBM by default. The user must opt in using the extension's settings. But priveleged extensions that are not loaded temporarily -- e.g. our final signed experiment extensions -- are granted access to PBM without the user's having to opt in [1]. So you need to be careful given your experiment's requirements and how you test it. It looks like there are some other subtleties too. For example, if you look above the line highlighted in [1], there's an `allowPrivateBrowsingByDefault` variable, and it's tied to an `extensions.allowPrivateBrowsingByDefault` pref [2]. [1] https://searchfox.org/mozilla-central/rev/cce8b90aece0f42e5025e45282de16066eeaa662/toolkit/components/extensions/Extension.jsm#2251 [2] https://searchfox.org/mozilla-central/rev/cce8b90aece0f42e5025e45282de16066eeaa662/browser/modules/ExtensionsUI.jsm#36
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One question that always comes up with experiments is how they should behave in private browsing mode. Depending on the experiment, we may want it to apply to both PBM and non-PBM, only non-PBM, only PBM, or way may want a different treatment between the two. The doc should call that out somewhere. The doc should also discuss some implementation subtleties. When an extension is loaded temporarily, it doesn't have access to PBM by default. The user must opt in using the extension's settings. But privileged extensions that are not loaded temporarily -- e.g. our final signed experiment extensions -- are granted access to PBM without the user's having to opt in [1]. So you need to be careful given your experiment's requirements and how you test it. It looks like there are some other subtleties too. For example, if you look above the line highlighted in [1], there's an `allowPrivateBrowsingByDefault` variable, and it's tied to an `extensions.allowPrivateBrowsingByDefault` pref [2]. [1] https://searchfox.org/mozilla-central/rev/cce8b90aece0f42e5025e45282de16066eeaa662/toolkit/components/extensions/Extension.jsm#2251 [2] https://searchfox.org/mozilla-central/rev/cce8b90aece0f42e5025e45282de16066eeaa662/browser/modules/ExtensionsUI.jsm#36