See the attached testcase. The call chain in the testcase is: ServoMediaRule::SetConditionText -> MediaList::SetMediaText -> ServoMediaList::SetText -> Servo_MediaList_SetText MediaList::SetMediaText calls MediaList::DoMediaChange to notify the document about the rule change, which is shared between Gecko and Stylo. I'm not sure what's going wrong here. The testcase is simplified from test_condition_text_assignment.html.

I have a patch that fixes the issue, I need to see if it's totally correct though.

Ended up being a lot simpler, patch incoming.

Comment on attachment 8847733 [details] Bug 1347381: Tell Servo earlier about stylesheet changes. https://reviewboard.mozilla.org/r/120660/#review122764

Pushed by ecoal95@gmail.com: https://hg.mozilla.org/integration/autoland/rev/2ab0ae532ebb Tell Servo earlier about stylesheet changes. r=heycam

Pushed by ecoal95@gmail.com: https://hg.mozilla.org/integration/autoland/rev/8a86967a1349 Adjust test expectations to account for new passes. r=emilio

https://hg.mozilla.org/mozilla-central/rev/2ab0ae532ebb https://hg.mozilla.org/mozilla-central/rev/8a86967a1349