DevTools: [Styles] Add all known unicode-bidi values to CSSMetadata

Add 3 more values, according to
http://dev.w3.org/csswg/css-writing-modes/#propdef-unicode-bidi

R=aandrey, eustas, vsevik
BUG=334096
NOTRY=true

Review URL: https://codereview.chromium.org/136153003

git-svn-id: svn://svn.chromium.org/blink/trunk@165074 bbb929c8-8fbe-4397-9dbb-9b2b20218538