Add test for sub-pixel scaling of web fonts

Add new test for scaling of web fonts with sub-pixel precision. Also
add a copy of the APL2 licensed OpenSans font to LayoutTests/resources/
opensans with LICENSE and README files.

R=dglazkov@chromium.org, eseidel@chromium.org
BUG=290411

Review URL: https://codereview.chromium.org/110853004

git-svn-id: svn://svn.chromium.org/blink/trunk@163663 bbb929c8-8fbe-4397-9dbb-9b2b20218538