Notable changes:
- javaScriptEnabled moved to the browser side.
- enabling new UI since it no longer helps to fix screencast
Review branch: https://github.com/aslushnikov/juggler/tree/roll-to-91-0-b10
Note: this will have 2 screencast tests failing. Investigation is in a follow-up.
When Firefox decides to perform an http->https redirect based on HSTS
information, it issues an "internal" redirect and cancels the http request.
Since there is no response for the http request, we forge 307 redirect
in this case, following Chromium lead.
The relevant code is in nsHttpChannel::StartRedirectChannelToHttps.
