Move DOMPoint/WebKitPoint to frame/

This code really should just be UMA'd and then removed.
It's only used by one webkit-proprietary interface on Window.

BUG=305811
TBR=abarth@chromium.org

Review URL: https://codereview.chromium.org/26963002

git-svn-id: svn://svn.chromium.org/blink/trunk@159405 bbb929c8-8fbe-4397-9dbb-9b2b20218538