I was conflating two different things: loading extensions and giving them access to privileged APIs. I think this does a better job of explaining things.
Differential Revision: https://phabricator.services.mozilla.com/D45931
Replace the "is heuristic?" logic for hiding keywords in keyword offers with something more flexible. Here's how the top sites extension uses this new `keywordOffer` payload property: 8408d13d2f
When a result's title is hidden, use the title color for the secondary color.
Differential Revision: https://phabricator.services.mozilla.com/D40898
* Move AddressBar.rst into a new browser/components/urlbar/docs directory
* Break it up into several files, which makes the patch look way bigger than it really is because I used `hg cp` to preserve blame
* Add an Experiments & Extensions file/subsection, to be written later
* Rewrite the intro a little for wording and also to reflect the fact that quantumbar has shipped, and also tweak the wording of some subsection titles
Differential Revision: https://phabricator.services.mozilla.com/D38938
