New chromium-mac pixel baseline for gradient-background-leakage-hidpi.html
https://bugs.webkit.org/show_bug.cgi?id=106373

Unreviewed gardening.

* platform/chromium-mac/fast/backgrounds/gradient-background-leakage-hidpi-expected.png: Added.

git-svn-id: http://svn.webkit.org/repository/webkit/trunk@139288 268f45cc-cd09-0410-ab3c-d52691b4dbfc