Media query malformed when 'or' is used as a media type.

The Media Queries errata[1] dated 2013-06-27 includes 'or' in the list of
reserved keywords that will result in a malformed media query instead of an
unknown media type when used as a media type.

[1] http://www.w3.org/Style/2012/REC-mediaqueries-20120619-errata.html

BUG=288213

Review URL: https://codereview.chromium.org/23477048

git-svn-id: svn://svn.chromium.org/blink/trunk@158713 bbb929c8-8fbe-4397-9dbb-9b2b20218538