Displays a notification above the composebox in cases where the message
is not visible (further down), or where it's outside the current narrow or search.
It also offers a link to the appropriate narrow when it makes sense, and offers
timetravel when appropriate. There is currently a bug with timetravel (and you can
see this when using the popover menu) that makes "narrow to messages around this time"
not work for muted messages.
This resolves Trac #1518.
(imported from commit 391ca0b9c07d91496f6585a4fd8e15723d1170e2)
acrefoot
Tim Abbott