Disable the newlines.vtt WebVTT parsing test

To be enabled after re-importing with the correct (mixed) line endings.

BUG=318734

Review URL: https://codereview.chromium.org/61793012

git-svn-id: svn://svn.chromium.org/blink/trunk@161932 bbb929c8-8fbe-4397-9dbb-9b2b20218538