Code review comment for lp://staging/~allenap/launchpad/ui-convert-bug-tracker-3.0-bug-418155-pt2

To walk through the UI, try:

 * Go to the bug trackers page (for IBugTrackerSet) at
   <https://bugs.launchpad.dev/bugs/bugtrackers>,

 * There's nothing new in this page for this branch, so just click on
   "This Mozilla.prg Bug Tracker" to see its overview page,

 * Look at the portlets. The top portlet replicates some of the info
   that's in the page, but it is used elsewhere in Launchpad so it's
   useful to keep.

 * Click "Change details",

 * This is one place where the details portlet is useful.

 * Use the new cancel link to return to the previous page,

 * Notice the new h1 title and h2 "Summary" heading,

 * Append /42 to the URL and see the remote bug index page, including
   the h2 "Is watched by..." and the new text. I think the text is
   good, but the heading was a tough one. I'm simply still not sure
   exactly how to use the heading slot.