Previously, if you had a generated background image and a translucent (or
rounded) border, we would draw the image nine times because we would inflate
the fill rect to draw behind the border. With no-repeat, we only draw the image
once.

This saves 4.5% of record time on flights-app.

R=esprehn@chromium.org

Review URL: https://codereview.chromium.org/844193009