Disable ScrollingCoordinatorChromiumTest.rtlIframe on Windows

BUG=311425
TBR=falken@chromium.org

Review URL: https://codereview.chromium.org/42683002

git-svn-id: svn://svn.chromium.org/blink/trunk@160506 bbb929c8-8fbe-4397-9dbb-9b2b20218538