bug#16028: 24.3.50; Latest build completely breaks my thumnail frames code

[martin rudalics]

> Running it through the debugger, I see that the frame _is_ shrunk
> correctly, along with the font, at this point in the code:
>
> (enlarge-font (- thumfr-font-difference) frame)
> ...
> (modify-frame-parameters frame thumfr-frame-parameters)
>
> But if I don't go through the debugger, it does not work.  And if I just
> hit `c' in the debugger, instead of `d' throughout, it also does not work.
>
> This is 100% reproducible.  Dunno why stepping through the debugger would
> work, and even hitting `c' for the `enlarge-font' call works, but hitting
> `c' for the `condition-case' does not.

Put in some sit-fors.  Check whether and which exception handlers get
called.  Check which frame parameters get set and reset.

martin