Created attachment 8885788 [details] before mouse over In Google Docs the star is no longer visible until you mouse over it and then its visible and remains until reload.
I think I have seen a similar issue where mousing over some Google Docs buttons or the "Last edit was on ..." label would show a tooltip that would not disappear when I stopped mousing over. I could not reproduce it consistently so I wasn't able to determine if it was related to Stylo or just a Google Docs timing issue.
It seems to me that there is always a significant time before the star shows up, both in Gecko and Stylo, so I don't see any difference in this case...
The star doesn't show up in the stylo case, no matter how long I wait. I tested this with DevEdition and the star appears as soon as the other elements render.
I can reproduce this. The star never shows up in Stylo (until hovered), unlike Gecko which will eventually show up in a few seconds. I'll take a look into this.
The star is a ::before pseudo element with "content: url(//ssl.gstatic.com/ui/v1/star/star4.png);". In stylo the pseudo element is not created until hovered. The hover adds a "jfk-star-hover" class to the container element, creates the ::before pseudo element and loads a different png (star4-hover.png). Then the un-hover event will trigger the loading of the "star4.png" file. In Gecko the pseudo element is created on first load.