Expose "session history" in Session

[pocmo]

Reference browser user story: mozilla-mobile/reference-browser#69

To be able to render the "history" of a single Session we will need to expose this list in the Session itself.

Unclear is where this data should come from.

• WebView has copyBackForwardList().
• GeckoView doesn't seem to have anything like that yet.

┆Issue is synchronized with this Jira Task

[pocmo]

May need a GeckoView API. Currently snorp says we could implement this on our own by using the HistoryDelegate. However I am a bit concerned that we will have issues keeping the GeckoSession history stack and our own list in sync.

[pocmo]

https://bugzilla.mozilla.org/show_bug.cgi?id=1509110

[pocmo]

After discussing this with the GV team the consensus is that GV will provide APIs for:

• Getting the history list of a GeckoSession.
• Getting the current index (in the list) the session is at
• Navigating to a specific index (this is something we'd implement in a different issue)

[pocmo]

mozilla-mobile/firefox-tv#1558

[bifleming]

@vesta0 this is still in the 'blocked' column on teh A/C sprint board... should it be moved? But is it post-MVP? we should take everything that is Post-MVP off of that board I think.

[jonalmeida]

This would be needed for supporting the tab history for sync tabs.

[jonalmeida]

This seems mostly for "read" access to the history stack, but we would need a way to add to it.

It isn't blocking sync tabs, but would be eventually needed to land the final feature.