Currently eclipse-swt is built against webkit2gtk-3.0. Please switch to webkit2gtk-4.0 for F21; the API changes are minimal and likely no code changes are required besides changing the pkg-config invocation to use the new version. webkit2gtk-4.0 is in the webkitgtk4-devel package.
Sami, please take care of this one.
Kalev, thanks for fixing the build :)
Thanks guys!