Added labs/desktop_capture_iframe_version.js and some changes to easyrtc_int.js to support it. This supports using Muaz Khans iframe solution for a single extension for all domains. It is primarily aimed at those who want to try out desktop capture without creating their own extension. It needs additional work to install the extension if it is not already installed. Upcoming work will support an alternate iframe-less solution that uses a google desktop capture extension that is specific to a domain (what you should use in a production environment). Your page must still be hosted on an https server.