Mark back-to-javascript-url-iframe.html as Pass Timeout for debug

TBR=japhet@chromium.org
BUG=

Review URL: https://codereview.chromium.org/69183002

git-svn-id: svn://svn.chromium.org/blink/trunk@161735 bbb929c8-8fbe-4397-9dbb-9b2b20218538