Remove feature that is no longer used by blink as the Android port now turns fixed backgrounds into layers rendering this code obsolete.
    
BUG=none

Review URL: https://codereview.chromium.org/59763011

git-svn-id: svn://svn.chromium.org/blink/trunk@161821 bbb929c8-8fbe-4397-9dbb-9b2b20218538