Make slow-loading-image-in-pattern.html not use an expected result file.

It was using the expected result from a different test in the test itself.
Instead copy an expected result file into the resources directory and use that.

TBR=adamk@chromium.org

Review URL: https://codereview.chromium.org/22962006

git-svn-id: svn://svn.chromium.org/blink/trunk@156044 bbb929c8-8fbe-4397-9dbb-9b2b20218538