Ignore changes to mixed content blocker state during startup

For some reason firefox 26 sets block_active_content to false and then true,
which was inducing:

https://trac.torproject.org/projects/tor/ticket/10344
Measure startup performance time in Chrome.
Implement a test for ruleset querying performance
Most targets don't match without a preceding www. !?

Also comment out logging calls that might bias test results.

Conflicts:
	src/chrome/content/code/HTTPSRules.js
Take measurements in milliseconds; count hits
Make prefixing explicit
Only run performance tests if an about:config variable is set
Merge branch 'master' of git://git.torproject.org/https-everywhere