[CHROME] add a power-user setting to re-enable mixedcontent rulesets
Rulesets disabled due to legacy/trac#6975 (moved) may still be useful to power users who prefer to look at things in HTTPS even if the CSS and/or JS is all messed up.
We should add a Chrome settings option to say "Force HTTPS even on sites that render weirdly if they are forced to be secure".
It should have a rollover/tooltip which explains that this is about embedded CSS/JS, and points to the shield in the URL bar.