One hour of reading DXR later and I *think* I want to get the timestamp of this: https://dxr.mozilla.org/mozilla-central/source/layout/base/nsPresShell.cpp#3809
or something around it :) as this will tell me a couple of things: 1) Things injected into DOM after this timestamp may/will cause reflow. 2) Things injected into DOM before this timestamp are unlikely to cause FOUC 3) If I change any code in ContentSink, HTMLParser, or if I'll inject a MutationObserver that will be catching nodes as the Parser feeds the DOM and modifying them, I should see this timestamp being affected and in result performance being impacted. Does it sound like what I'm looking for? zb. _______________________________________________ dev-platform mailing list dev-platform@lists.mozilla.org https://lists.mozilla.org/listinfo/dev-platform
