Remove NodeIsSupported from UseCounter.h

I forgot this in r165237: https://codereview.chromium.org/133703014

BUG=334970

Review URL: https://codereview.chromium.org/173813003

git-svn-id: svn://svn.chromium.org/blink/trunk@167558 bbb929c8-8fbe-4397-9dbb-9b2b20218538