This reuses the newly introduced infrastructure to track painting, and
avoids painting if rendering is suppressed (such as for view transitions
and so on).
Rendering suppression of an in-process iframe needs more work because
right now we paint in-process iframes as part of the top document's
display list.
Remove some old paint invalidation printf-debugging, which I suspect
nobody has used in years. Profiler markers are strictly better :)
Differential Revision: https://phabricator.services.mozilla.com/D245063
327d527c49