DevTools: Unify protocol test scripts naming with frontend tests.

R=lushnikov@chromium.org, lushnikov, pfeldman

Review URL: https://codereview.chromium.org/183663014

git-svn-id: svn://svn.chromium.org/blink/trunk@168370 bbb929c8-8fbe-4397-9dbb-9b2b20218538