Add UseCounter for DOMFocusIn and DOMFocusOut event listeners.

They are obsolete names defined in DOM Level 2, and neither IE nor Firefox has
them.

BUG=

Review URL: https://codereview.chromium.org/102643003

git-svn-id: svn://svn.chromium.org/blink/trunk@163199 bbb929c8-8fbe-4397-9dbb-9b2b20218538