Remove deprecated two argument overload of WebFrame::create().

There are no remaining callers to this overload, so we can
remove it.

BUG=none
R=eseidel@chromium.org

Review URL: https://codereview.chromium.org/175463004

git-svn-id: svn://svn.chromium.org/blink/trunk@167641 bbb929c8-8fbe-4397-9dbb-9b2b20218538