https://bugs.webkit.org/show_bug.cgi?id=124489

Reviewed by Philippe Normand.

In r158821, several properties were changed from readonly to
CustomSetter. The GObject DOM bindings currently skips any
attribute having a custom getter or setter, and those properties
are not generated anymore. We should add support for generating
attributes having a custom getter or setter in GObject DOM
bindings generator, but to fix the ABI break now we bring the old
implementatiom back as custom implementation. This fixes the ABI
compatibility, but not the API since the GObject properties are
not generated.

* bindings/gobject/WebKitDOMCustom.cpp:
(webkit_dom_audio_track_get_kind):
(webkit_dom_audio_track_get_language):
(webkit_dom_text_track_get_kind):
(webkit_dom_text_track_get_language):
(webkit_dom_video_track_get_kind):
(webkit_dom_video_track_get_language):
* bindings/gobject/WebKitDOMCustom.h:
* bindings/gobject/WebKitDOMCustom.symbols:

git-svn-id: http://svn.webkit.org/repository/webkit/trunk@159411 268f45cc-cd09-0410-ab3c-d52691b4dbfc