Use FINAL macro for classes whose virtual destructor was removed

Use FINAL macro for classes whose virtual destructor was removed, to make sure
no one tries to subclass them in the future.

BUG=311561

Review URL: https://codereview.chromium.org/47613002

git-svn-id: svn://svn.chromium.org/blink/trunk@160852 bbb929c8-8fbe-4397-9dbb-9b2b20218538