Distinguish between antialiased and non-antialiased reference images.

Tested locally with and without --disable-gl-multisampling flag.

BUG=330053
TBR=dtu@chromium.org

Review URL: https://codereview.chromium.org/112863005

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@242598 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 242598