As per summary, the downloadable fonts feature described here don't works with pango backend in my WebKit build (using jhbuild).
This seems a pango only bug: in fact trying midori browser installed by distro (using svn release 29752), the same feauture works fine. See attached screenshots.
Created attachment 20633 [details]
Downloadable fonts with Pango backend
The screenshots shows Epiphany running on recent (5~6 hours ago) WebKit checkout. I don't know if donwloadable fonts was downloaded, but of course wasn't used :-(
Created attachment 20634 [details]
Downloadable fonts with Freetype backend
To quickly check if this was a Pango only bug, I tried the same page with midori browser shipped with Ubuntu 8.04. WebKit installed by package libwebkitgtk1d_0~svn29752-1_i386.deb
Pango upstream is missing support to load fonts from memory -- I believe the bug was reported to b.g.o years ago but I don't have a reference to hand. The Pango backend can't become the default until this is fixed.
Updated WebKit module on jhbuild to not force pango backend.
Alp, we could open a new pango bug...
This is http://bugzilla.gnome.org/show_bug.cgi?id=347237
There is no longer a Pango backend after http://trac.webkit.org/changeset/137263.