Happens for the map at Google Flights (https://www.google.de/flights/) that is the No 1 search result when googling for Flights (that's of course a clever move by Google to create a top site that only works fine with Chrome, I wonder how long it will take that YouTube or GMail only work "optimal" with Chrome)
Anyway, I filed https://bugzilla.mozilla.org/show_bug.cgi?id=1329141 but this is only P3 priority (that is, marked a "valid" bug but nobody is working on it). Which I found really "strange" because website not working in Firefox and being force to temporally switching to Chrome (and maybe staying) are the worst that can happen. Eventually, when booking a flight I even had to tell other family members that they should use Chrome for it (who were surprised because normally I tell them to use Firefox ;)