The header file webkit-3.0/webkit/webkit.h contains #include <webkit/webkitglobals.h>, but the webkitglobals.h file is not installed by "make install". This breaks the build for any program using WebKitGTK+ (e.g. Epiphany). I'm using today's git master, fwiw.
I believe that I fixed this earlier today. Feel free to re-open if the problem persists. Thanks for reporting!