I tracked this problem down to having enabled strict isolation mode
in response to a recommendation at the time meltdown was announced.
As far as I can tell this is still the only option for protecting
aginst meltdown/spectre attacks within chromium, so it's not great
to have to disable it, but I'd be happy to be corrected.
I disagree with the new severity of minor, as this bug certainly does
affect the package's usefulness - I just had to switch to firefox to
print a web page to PDF.