Remove the -webkit-marquee shorthand

This is a first step towards unexposing the prefixed marquee
properties. -webkit-marquee is the only pure CSS property (and
a shorthand for the other prefixed properties) so it will help
find any issue that could come from the following un-exposures.

BUG=274055

Review URL: https://chromiumcodereview.appspot.com/22810009

git-svn-id: svn://svn.chromium.org/blink/trunk@156233 bbb929c8-8fbe-4397-9dbb-9b2b20218538