We currently require support for IntersectionObserver.
which is supported on Edge >= 15 (15 has partial support),
Firefox >55, Chrome >58, Safari 12.1, Opera >=38,
iOS Safari >=12.2, Android 100
Full ES6 is supported in Edge >=15, Firefox >=54, Chrome >=51,
Safari >=10, Opera >=38, iOS Safari >=10, so such a change
would only drop support for Edge 15 and Firefox 54.
CSS.escape is guaranteed in all these browsers according to
caniuse, with the only discrepancy being the Edge browser (versions
16-18) so it is also suggested we remove support for those browsers.
Firefox 54 accounts for 0.0026% of page views
Edge 15-18 accounts for 0.069% of page views
Bug: T306355
Change-Id: Id2987e3456607b610c38da9ee157a026d1d00ada
useful for testing real world data
Suggested test config:
```
$wgRelatedArticlesUseCirrusSearchApiUrl = "https://en.wikipedia.org/w/api.php";
$wgRelatedArticlesUseCirrusSearch = true;
$wgRelatedArticlesDescriptionSource = 'wikidata';
```
This will allow us to enable on patchdemo with production content.
Change-Id: I73c0d73d3369f27ed2fd74b37ae71bfc12b6ee57
The RelatedPagesGateway is an OO class.
There is no reason for it to be, we don't use any
of it's features e.g. the event emitter
Change-Id: I8f807d35b0ce36ea5764508a66f88d74577e3653