WebKitGtk+ erases background before loading a new page. So, if it takes some time to load the page, users have to see the empty page for a second. This makes the user think that the page loading is very slow. However, in the case of other WebKit based browser, they leave the current page before preparing the layout of a new page, and then just replace the current page with the new one.
Created attachment 90968 [details] Propsed Patch
Comment on attachment 90968 [details] Propsed Patch Isn't finishedLoad extremely late for us to attach the adjusments?
OK, this is the load finished for the DOM Document, not for the whole thing, I think. I believe Martin is working to remove the need to attach adjustments entirely in any case, so perhaps we want to wait for that.
Comment on attachment 90968 [details] Propsed Patch Going to r- this one now, as hopefully in a few days we won't need to attach adjustments at all. If that approach fails though, please ping me later and we can re-address this one.
#59821 fixed this issue.