Adjust expectations for form layout tests. Only Linux and Win affected.

TBR=sky@chromium.org
NOTRY=true
BUG=417625

Review URL: https://codereview.chromium.org/598373002

git-svn-id: svn://svn.chromium.org/blink/trunk@182663 bbb929c8-8fbe-4397-9dbb-9b2b20218538