STR: 1. Load about:about 2. Zoom in to 110% 3. Move the mouse around or click on the address bar Actual results: The page goes blank. Moving the mouse over the page content causes some of the links to briefly appear and then disappear again. Expected results: Normal rendering. This appears to be a recent regression.

The symptoms happen in some other sccenarios as well, such as Responsive Design Mode.

Mozregression points to bug 1413546: https://hg.mozilla.org/integration/autoland/pushloghtml?fromchange=873f58fff17d0551455eeb36614b91d197c47dbc&tochange=716d49302a28f9231c628a1dca5a744437403948 Miko, could you have a look please?

[Tracking Requested - why for this release]: Serious rendering issue on parent-process pages such as about: pages and Responsive Design Mode. Bug 1413546 landed just after the merge, so 63 is not affected.

The problem here seems to be that nsDisplayZoom item inside nsDisplaySubDocument disappears randomly. It seems worthy to note that this feature can be disabled at any point by flipping layout.display-list.retain.chrome to false.

The cause for the items disappearing is that nsDisplayResolution and nsDisplayZoom inherit from nsDisplaySubDocument, but do not set member variable |mSubDocFrame|, which causes nsDisplaySubDocument::HasDeletedFrame() to return true.

Comment on attachment 9006719 [details] Bug 1488889 - Pass nsSubDocumentFrame to nsDisplaySubDocument constructor Matt Woodrow (:mattwoodrow) has approved the revision.

Pushed by mikokm@gmail.com: https://hg.mozilla.org/integration/autoland/rev/d7df7b04f55a Pass nsSubDocumentFrame to nsDisplaySubDocument constructor r=mattwoodrow

Thanks for the quick fix!