== Background
The Fundraising team will be running tests every Wednesday, throughout August. Because their analysts don't believe that we should apply the results from the previous test on itwiki to other wikis, the Fundraising team have requested that Page Previews re-expose whether previews are enabled so that it can be included in the analysis of the new tests.
== AC
If the Popups extension is loaded on the wiki, then:
[] `mw.popups.enabled` variable is set to `true` when previews are enabled for the user; otherwise, it's set to false.
[] This is the case for all users.
== Developer Notes
* We talked about implementing this as a ES5 property access with a getter but not a setter, so that it is clear that the global variable is read only and cannot be set to manipulate popups. Also we are keeping the `mw.popups.enabled` interface so that the fundraising team don't have to update their code. Pseudocode:
```lang=js
mw.popups = {}
Object.defineProperty(mw.popups, 'enabled', {
get: function() { return store.getState().preview.enabled; },
set: function() { throw new Exception('You can\'t set mw.popups.enabled'); }
});
```
* Also @phuedx mentioned using the getter to return the data from the store directly, instead of having to implement a change listener.