Adding regression test for a small caps layout issue on Mac

The test uses the Libertine font, licensed under the Open Font License
as a free font example that comes with small caps.

BUG=264372
TBR=dpranke,eae

Review URL: https://codereview.chromium.org/144093011

git-svn-id: svn://svn.chromium.org/blink/trunk@165633 bbb929c8-8fbe-4397-9dbb-9b2b20218538