Fixed position layers don't move, so it doesn't make sense to try to retain tiles. Currently, it just ends up causing weird-looking rendering glitches. We should just not use them for fixed position layers. Eventually retained tiles will be superseded by on-demand tile rendering work, but this is an easy thing to do that will improve the experience on sites with top/bottom bars, etc.
Created attachment 651516 [details] [diff] [review] Don't retain tiles on fixed position layers
Comment on attachment 651516 [details] [diff] [review] Don't retain tiles on fixed position layers r+, nice detailed comment.
Pushed to inbound: https://hg.mozilla.org/integration/mozilla-inbound/rev/84f253d1174c
Comment on attachment 651516 [details] [diff] [review] Don't retain tiles on fixed position layers [Approval Request Comment] Bug caused by (feature/regressing bug #): Rendering artifacts when panning/zooming on pages with fixed-position elements User impact if declined: See above Testing completed (on m-c, etc.): Tested locally Risk to taking this patch (and alternatives if risky): Low - just disables a feature in a simple and reliable way. String or UUID changes made by this patch: None
Pushed to aurora: http://hg.mozilla.org/releases/mozilla-aurora/rev/bb764cfc347a