Remove some dead code from css/ folder

Remove some dead code from css/ folder. Several methods / members were defined
but never used.

R=ojan@chromium.org,jchaffraix@chromium.org

Review URL: https://codereview.chromium.org/241363003

git-svn-id: svn://svn.chromium.org/blink/trunk@171905 bbb929c8-8fbe-4397-9dbb-9b2b20218538