Fenix: Allow third-party apps to open a tab in private browsing mode

[Low012]

Previous versions of Firefox (until including version 68.11.0) allowed third party apps allowed third party apps to open tabs in private browsing mode by adding the extra "private_tab" to an Intent.

The original request for Fennec can be found in https://bugzilla.mozilla.org/show_bug.cgi?id=1347583

This feature is missing from Fenix. It only seems to be possible to open links from external when this behaviour is enabled in the settings, but in this case _all_ links are opened in private tabs. The behaviour cannot be managed by third party apps.

The check for private mode is done in https://github.com/mozilla-mobile/fenix/blob/master/app/src/main/java/org/mozilla/fenix/IntentReceiverActivity.kt#L47

It may be sufficient to change the line

val private = settings().openLinksInAPrivateTab

to

val private = settings().openLinksInAPrivateTab || intent.hasExtra(PRIVATE_BROWSING_MODE)

[kbrosnan]

The open links in private tabs setting provides this feature.

[Low012]

Not really, the user story is different.

Fenix implements: "As a user I want to be able to determine if URLs opened from external apps will open in a private tab or not for all third party apps."

What was possible in previous versions of Firefox: "As a developer of a third party app I want to be able to determine if URLs opened from my app will open in a private tab or not."