DevTools: remove dead WebKit-based test support.

R=sergeyv@chromium.org
TBR=vsevik

Review URL: https://codereview.chromium.org/172163006

git-svn-id: svn://svn.chromium.org/blink/trunk@167584 bbb929c8-8fbe-4397-9dbb-9b2b20218538