[HTTPS-Everywhere] Allowing rulesets or ruleset defaults to be platform-dependent

[Peter Eckersley]

It looks like we will need a way to say that some rewrite rules apply in
Firefox but not Chrome:

https://trac.torproject.org/projects/tor/ticket/5196
https://trac.torproject.org/projects/tor/ticket/5224

It isn't clear yet whether we should do that the "lazy" way, by having a
separate Chrome git branch, or the "more elegant" way, by adding an extra
attribute to the XML format to indicate platform specificity.  

If we go the XML road, we could add a <ruleset> attribute to control which
rulesets are on/off by default on various platforms; or a <rule> attribute to
say that certain rewrites only happen on some platforms; or both.

Doing something at the <ruleset> level might allow us to handle other cases
like the fact that some platforms trust the CACert root and others do not:

https://trac.torproject.org/projects/tor/ticket/3776

-- 
Peter Eckersley                            pde at eff.org
Technology Projects Director      Tel  +1 415 436 9333 x131
Electronic Frontier Foundation    Fax  +1 415 436 9993