[KevinH]

After staring that the blink renderer code for some time, it is clear a bad/partial merge from Chrome was introduced into Qt 5.12.8 and Qt 5.12.9. Somebody reversed a test condition to make it easier to understand but forgot to swap the then and else clauses and as a result completely reversed the logic in places.

I checked the Chrome 80 sources and this bug does not exist (the if test was reversed as were the then and else clauses) so that explains why Qt 5.15 seems to work.

I have now fixed that bug and I am rebuilding Qt once again to see if this fixes our issue or if there is more breakage that needs to be tracked down.

What a mess!