win: Now that we're on msvs2013, spell final 'final' not 'sealed'.

Part 2 of 3.
Part 1: https://codereview.chromium.org/224763005/

BUG=none
NOTRY=true

Review URL: https://codereview.chromium.org/224833004

git-svn-id: svn://svn.chromium.org/blink/trunk@170868 bbb929c8-8fbe-4397-9dbb-9b2b20218538