Support UseCounter in dedicated workers.

BUG=376039
R=haraken@chromium.org, sigbjornf@opera.com, tyoshino@chromium.org

Review URL: https://codereview.chromium.org/342103003

git-svn-id: svn://svn.chromium.org/blink/trunk@176511 bbb929c8-8fbe-4397-9dbb-9b2b20218538