Committed, adding a test about 'this', which is failing in Gnash.
Will track the 'this' issue next.

Yes, calling the function directly should be fine.

I had a quick go at finishing the array.sort(compareFunction) implementation since most of the work had already been done. I also added a test for it in the array.as (see attached patch).

The patch is a little more complex than I would have liked because I found that I had to pass in an as_object* "fn.this_ptr" to the call_method when invoking the compareFunction (passing in NULL resulted in assert failures). I suspect there might be a way to avoid this.

Also I'm not sure if call_method should be used in preference to the original idea of directly invoking the function on a fn_call object (either works, I leaned toward the call_method approach since it is already used in the code-base for a similar task [see timers.cpp]). If the fn_call approach is used, the stack_offset (last argument) should be set to 1 not 0 (and obviously the as_object* first argument changed from NULL).