Debugging firefox (0.9.3) on unix: Is there a documentation of the "mozilla object tree"?

Hi there!

I am trying to find/fix the mozilla-bug #236596 (aka #253992, i. e.
"Focus problem" when generating "forms" using client-side XSLT)
and I have "decided" to do this by debugging the code.

Following the instructions on

   http://www.mozilla.org/unix/debugging-faq.html

I managed to create a "debug-build" of mozilla-firefox-0.9.3
(and glibc) on my gentoo box.

Debugging the code now works with
   - "pure gdb"
   - "ddd" using "gdb" (that is what I prefer at the moment)
   - "emacs" and even
   - "anjuta" (but not very stable)
even without using the "prun" macro (set auto-solib-add 0),
maybe because of current (6.0) gdb-version or because of 512MB memory...

Setting breakpoints, stepping through the code (of "docshell/...",
"content/...", etc.) is what I have achieved so far.

What I haven't found out is the following:

   * Which parts of the code (which objects) are responsible for which "functionality"?
   * Especially, which objects handle (keyboard) focus?

Maybe this information (a "mozilla object tree") is available and I haven't found it
or such information is not required to trace "focus handling" when opening
my "testcase".

At the moment I am stuck.
Assistance, i. e. some hints and/or/on suitable documentation would be very appreciated. :-)

Thanks,

-- Axel (XL)