Auto merge of #3621 - moz-gfx:__wrlastsync, r=moz-gfx
Auto merge of #3621 - moz-gfx:__wrlastsync, r=moz-gfx

Sync changes from mozilla-central

servo/webrender,servo/webrender,servo/webrender,servo/webrender,servo/webrender,servo/webrender