Follow-up to script element moving fix (r184455).

This CL adds a test and also fixes the fix.

BUG=427108

Review URL: https://codereview.chromium.org/680263002

git-svn-id: svn://svn.chromium.org/blink/trunk@184508 bbb929c8-8fbe-4397-9dbb-9b2b20218538