Think more about activity sorting

[ianb]

So now we sort pages based on when they were first loaded. This is kind of reasonable. Except that a page you leave open for a long time – but don't close! – can end up pretty far down the list. Stupid things like interstitial search pages can easily push it below the fold.

What should we sort on? Should we lift things based on activity, not just the initial load? Should we try to keep track of what's above the fold and curate that a little? I worry if we lift based on any activity that we'll have too much movement, things constantly popping up, especially if two people are both being active (like switching tabs a lot – easy to imagine in a triage situation, for instance).

Curating the above-the-fold list wouldn't be that hard, except to determine quite how large that list is.

[ianb]

Let's revisit this after we compact the activity stream items a bit, getting icons in, and combining shared tabs into a single activity.