thanks, that lets me trace the generated code precisely
looks like the 2nd error is leading directly to the 3rd error you showed. i assume you're using a Chromebook from/in the US, and just with English as a configured language ?
in that JS console you opened, please try running this. i formatted it so you can copy & paste it as a single line.
l=console.log;try{l('lib.i18n.browser_',lib.i18n.browser_);}catch(e){l(e)};try{l('lib.i18n.browser_.getAcceptLanguages',lib.i18n.browser_.getAcceptLanguages);}catch(e){l(e)};try{l('lib.i18n.browser_.getAcceptLanguages()',lib.i18n.browser_.getAcceptLanguages(l));}catch(e){l(e)};try{l('chrome.i18n',chrome.i18n);}catch(e){l(e)};try{l('chrome.i18n.getAcceptLanguages',chrome.i18n.getAcceptLanguages);}catch(e){l(e)};try{l('chrome.i18n.getAcceptLanguages()',chrome.i18n.getAcceptLanguages(l));}catch(e){l(e)};
then copy & paste the output here. the last few lines *should* look like ['en-US', 'en'], but if you aren't getting that, something is funky.
-mike