STR: open a new tab, type in about:protections or about:studies.
AR: see a white screen for a long time, eventually the page will load

• page will instantly load if you open dev tools, resize the page, or click to a different tab and back.

ER: page should load with no delay.

I've been seeing this at least a week, reproduces reliably, but not always (~70%). Reproduces most often when it is a new tab, vs navigating from a different page.

I've seen this on Mac and Linux on 71.

Attached screen recording of the issue.

cc'ing nika, since the WindowGlobalParent thing reordered some document initialization stuff, and this also involves process flipping.

This seems to be duplication of Bug 1580604

Regression window:
https://hg.mozilla.org/integration/autoland/pushloghtml?fromchange=7a484d560816d3e468d41e67672f6edd99e787e4&tochange=b5ef2b8f7c2b739502c441a776e3266b53d10f5d

Regressed by; Bug 1542415

Looks like there were some regressions from turning on the frameloader-rebuilding changes. Any chance you could look into this kmag?

I think I'm just going to turn it off in non-Fission windows again, for now. It won't block any Fission work, since it will stay enabled for Fission loads regardless of the pref.

(In reply to Kris Maglione [:kmag] from comment #5)

I think I'm just going to turn it off in non-Fission windows again, for now. It won't block any Fission work, since it will stay enabled for Fission loads regardless of the pref.

Did it happen in another bug? Thanks

https://bugzilla.mozilla.org/show_bug.cgi?id=1580604#c3

(In reply to Pascal Chevrel:pascalc from comment #6)

(In reply to Kris Maglione [:kmag] from comment #5)

I think I'm just going to turn it off in non-Fission windows again, for now. It won't block any Fission work, since it will stay enabled for Fission loads regardless of the pref.

Did it happen in another bug? Thanks

Yes.