Gardening: marking image-zoom-to-25.html as failure

It most likely just needs a rebaseline after the "Subpixel precision"
patch: https://codereview.chromium.org/267723002

BUG=369376,27987
TBR=eae,eseidel

Review URL: https://codereview.chromium.org/265883006

git-svn-id: svn://svn.chromium.org/blink/trunk@173163 bbb929c8-8fbe-4397-9dbb-9b2b20218538