I made two commits related to this bug (it'll be just one the next time).
Note that this feature is optional in Firebug and so, you need to set the following pref to true:
Also, the MozAfterPaint event is no longer sent to web content by default for the time being; it is still sent to chrome, however (there is a potential security issue; see bug 608030 for details). Until that's resolved, you can enable delivery of MozAfterPaint by setting the preference dom.send_after_paint_to_content to true.
Yet reopening, related data are not properly sent in case of remote monitoring
Now fixed even for the remote scenario