STR: 1. Open http://www.arvrgarage.nz/ in Firefox 64 (currently in beta) 2. Wait for it to load... 3. Observe weird rendering of the backdrop behind the "The Garage" div. This appears to have regressed in 64, as the site displays correctly in 63 Release.

This bug only repro's when WebRender is enabled, so triaging appropriately.

mozregression --good 2018-08-01 --bad 2018-11-14 --pref gfx.webrender.all:true -a http://www.arvrgarage.nz/ > https://hg.mozilla.org/mozilla-central/pushloghtml?fromchange=87ae93caad9b0c48edaf349633c275e4e0059e9e&tochange=e088bb62f286425a30a925fc3355eb40c92f79c1 mozregression --repo mozilla-inbound --good 1cae5a527a4b --bad 6807afe94107 --pref gfx.webrender.all:true -a http://www.arvrgarage.nz/ > 5:47.24 INFO: Last good revision: be6801cdeb537afa655bbd67d12ead8dc01c6c38 > 5:47.25 INFO: First bad revision: 302dcd8139426cfe25b9d2685800809c2d603658 > 5:47.25 INFO: Pushlog: > https://hg.mozilla.org/integration/mozilla-inbound/pushloghtml?fromchange=be6801cdeb537afa655bbd67d12ead8dc01c6c38&tochange=302dcd8139426cfe25b9d2685800809c2d603658 > 302dcd813942 Andrew Osmond — Bug 1485420 - Part 2. Make ClipManager trim clip chains which can be merged with the display item. r=mstange > a3ea43b5e6d8 Andrew Osmond — Bug 1485420 - Part 1. Expose WebRender bindings to merge a clip rect with a display item. r=mstange This could be a duplicate of bug 1499015.

mozregression --find-fix --bad 2018-11-14 --good 2018-11-19 --pref gfx.webrender.all:true -a http://www.arvrgarage.nz/ > 11:50.36 INFO: First good revision: 669cd919724934a05579ed2e561d04dedd11e93a > 11:50.36 INFO: Last bad revision: e58fd91eddcdbdf00c8a1902026c1d4fe0845396 > 11:50.36 INFO: Pushlog: > https://hg.mozilla.org/integration/autoland/pushloghtml?fromchange=e58fd91eddcdbdf00c8a1902026c1d4fe0845396&tochange=669cd919724934a05579ed2e561d04dedd11e93a > 669cd9197249 WR Updater Bot — Bug 1507848 - Update webrender to commit 5609676e166f939fcf1a4141c5b9cb715b68f1d9 (WR PR #3315). r=kats https://github.com/servo/webrender/pull/3315