Failures on [infra] Upgrade firefox to the latest stable

[athomas]

There are new test failures on [infra] Upgrade firefox to the latest stable.

The tests

co19/LibTest/html/Element/getBoundingClientRect_A01_t02 RuntimeError (expected Pass)
corelib/regexp/named_captures_2_test RuntimeError (expected Pass)

are failing on configurations

dart2js-linux-firefox
ddc-linux-firefox

[nshahan]

co19/LibTest/html/Element/getBoundingClientRect_A01_t02 I'm guessing this is a pretty old test that might need updating. I'll reassign to the web-libraries for investigation.

corelib/regexp/named_captures_2_test is already failing on chrome and safari so this failure actually brings more consistency in the regex implementations and there is already an issue tracking this test failure:
#50437