Customize the homepage for users that disable persistent PBM

From #40144 (closed): we've decided to redirect about:privatebrowsing, but we could do something else in the future for users that disable auto-PBM.

added UX Team Roadmap::Future UX labels

mentioned in issue #40144 (closed)

added Feature label

added Desktop label

assigned to @donuts

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added Icebox label and removed Roadmap::Future label

unassigned @donuts

@pierov you mean to say to have separate about:tor to signal to users they are in a private browsing session when they disable the default alwasy-on pb?

No, I think I meant the opposite: remind them they're not in PBM, and that disabling PBM isn't supported.

I wonder if this should be displayed as a warning in the chrome instead, since it's not a connection issue. Perhaps there's another precedent for a similar "you've broken your browser" warning in Firefox?

That seems good more for a one-time notification to me, and users will be mad at us if we add chrome warnings for this.

I was thinking about a warning in the homepage so that at least it's harder to confuse between PBM and non-PBM windows.

added Apps::Type::Enhancement label

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