WebRTC getIdentityAssertion blocked on background script

[Sparika]

The call to getIdentityAssertion from RTCPeerConnection in the background script is blocked. It may be due to several cause:

• CORS issue on moz-extension:// scheme
• Unauthorized script-src (IdP domain) in script

Current solution is to instantiate the RTCPeerConnection in a iframe from a weborigin (https).

Required update is at least to serve the iframe from the web (gh-page ?), rather than from localhost.

[Sparika]

RTCPeerConnection is now instantiated in the content-script. Simpler solution.