testing usability on some websites

• sync: the login phase hangs.
  • reproduced: no.
  • reproduced in firefox: no.
  • found root cause:
  • found a fix/workaround:
• soundcloud: cannot login, possibly because of RFP.
  • reproduced.
  • reproduced in firefox: yes, with RFP enabled.
  • found root cause: RFP fixes the user agent to ESR, which causes Google ReCaptcha to refuse loading.
  • found a fix/workaround:
    • disabling RFP.
    • reported upstream.
• hotels.com: the site does not load when RFP is enabled.
  • reproduced
  • reproduced in firefox: yes, with RFP enabled.
  • found root cause: it's RFP, specifically a performance.measure() thing.
  • found a fix/workaround:
    • disabling RFP.
    • already reported upstream.
    • allowing canvas access isn't enough.

locking as this is for me and I don't need external contributors atm.