DevTools: Remove orphaned CSS rules [5]

That was my fault.
See https://codereview.chromium.org/248883003

BUG=
NOTRY=true

Review URL: https://codereview.chromium.org/431983002

git-svn-id: svn://svn.chromium.org/blink/trunk@179374 bbb929c8-8fbe-4397-9dbb-9b2b20218538