Previously, narrowing would only work from recipient rows, not
other message table rows (e.g. summary rows). This led to the trap
that you could add a narrows_by_recipient class to an element,
expect that narrowing would work, but the actual handler would
break or silently fail if it weren't part of a recipient row.
Now the click handler looks for the closest table row (tr). It's
encapsulated in rows.get_closest_row(), so if we go to a
non-table-based design, it should be easy to address in one
place.
(imported from commit e116b7573c4bb06599ced84a0adcf8dc23d63593)
Steve Howell
Kevin Mehall
Scott Feeney
Tim Abbott