Remove unneeded destructors and add finalization support to various classes.

Issues reported by the Blink GC clang plugin.

R=haraken@chromium.org
BUG=

Review URL: https://codereview.chromium.org/184853006

git-svn-id: svn://svn.chromium.org/blink/trunk@168568 bbb929c8-8fbe-4397-9dbb-9b2b20218538