windowsKeyCodeForKeyEvent (in WebCore/platform/gtk/KeyEventGtk.cpp) handles GDK_Return but not GDK_ISO_Enter and GDK_KP_Enter. I will write a patch ASAP.
Created attachment 20663 [details] Handle GDK_ISO_Enter and GDK_KP_Enter in windowsKeyCodeForKeyEvent
Landed in r32245. patch had a little trouble with this one so I had to hand-apply.