bug#22048: 25.1; frame title vanishes when speedbar present

[David Reitter]

> 
> I'm afraid I don't follow: why does ns_set_name_as_filename need the
> buffer to be the current buffer?  It access that buffer through the
> frame pointer:

Yes, but x_implicitly_set_name reads Vframe_title_format directly:

if (FRAME_NS_P (f) && ((FRAME_ICONIFIED_P (f) && EQ (Vicon_title_format, Qt))
                         || EQ (Vframe_title_format, Qt)))

It picks up the wrong value there.  Based on that, I think 
ns_set_name_as_filename isn’t called at all because it reads the value meant 
for the speedbar frame. I didn’t bother to look at what then happens in 
ns_set_name and ns_set_name_internal.

We can of course use BVAR to read Vframe_title_format as a smaller change, but 
unless you tell me otherwise, it seems to make more sense to have the right 
buffer current when calling the port-specific routing.

(By the way, I first tried to do this in x_implicitly_set_name:

set_buffer_internal_1
        (XBUFFER (XWINDOW (f->selected_window)->contents));

which works, but I find that the more dangerous change as the current buffer is 
permanently changed.