-webkit-mask-repeat: round does not work

Manually add png files due to commit-bot problems

BUG=260691
Code review URL: https://codereview.chromium.org/19785003/

R=mkwst@chromium.org

Review URL: https://codereview.chromium.org/22353005

git-svn-id: svn://svn.chromium.org/blink/trunk@155606 bbb929c8-8fbe-4397-9dbb-9b2b20218538