Gardening: xmlhttprequest-timeout-worker-simple.html is flaky on Win

BUG=311467
TBR=jsbell

Review URL: https://codereview.chromium.org/43103002

git-svn-id: svn://svn.chromium.org/blink/trunk@160527 bbb929c8-8fbe-4397-9dbb-9b2b20218538