are you sure the problem is that Scaffold doesn't have atob? That'd be very odd -- it should have all javascript available in Firefox 54, which certainly includes atob.
I suspect the tests are failing because the built-in browser can't handle the semantic scholar website.

in any way, this is fine, thanks!

I get the below error, but it may be an artefact of the browser not loading the website (which is new & strange behaviour)

14:54:35 TranslatorTester: Running 1 test for Semantic Scholar
14:54:35 TranslatorTester: Running Semantic Scholar Test 1
14:54:36 TranslatorTester: Translating https://www.semanticscholar.org/paper/Foundations-of-Statistical-Natural-Language-Proces-Manning-Sch%C3%BCtze/06fd7d924d499fbc62ccbcc2e458fb6c187bcf6f
14:54:36 Translation using Semantic Scholar failed: 
         string => ReferenceError: atob is not defined
         stack => parseDocument/<@Semantic Scholar:95:5
...

Thanks for the merge :)

Translators in the Zotero client run in a sandbox, which didn't have atob. I've added it for the next version.