Remove unused methods from RefCountedBase.
Remove unused methods from RefCountedBase.

These methods were never used by the Chromium port, since they are
Mac-specific or JSC-specific.

Review URL: https://chromiumcodereview.appspot.com/14862003

git-svn-id: bf5cd6ccde378db821296732a091cfbcf5285fbd@149620 bbb929c8-8fbe-4397-9dbb-9b2b20218538

primiano/blink-gitcs,primiano/blink-gitcs,primiano/blink-gitcs,primiano/blink-gitcs,primiano/blink-gitcs,primiano/blink-gitcs,primiano/blink-gitcs,primiano/blink-gitcs,primiano/blink-gitcs