Create DEFINE_STATIC_REF macro and use it

Based on idea from James Robinson <jamesr@chromium.org>

The DEFINE_STATIC_REF is a DEFINE_STATIC_LOCAL analogue for ref-counted objects which allows however to obviate an unneded allocation when using 'DEFINE_STATIC_LOCAL(RefPtr<>..)'.

Review URL: https://codereview.chromium.org/66723005

git-svn-id: svn://svn.chromium.org/blink/trunk@161826 bbb929c8-8fbe-4397-9dbb-9b2b20218538