In bug 249750/258248@main I added Page:: willStartRenderingUpdateDisplay() and Page:: didCompleteRenderingUpdateDisplay(), which get called before and after the painting phase and compositing phase of a rendering update. These are used to drive web inspector's "Composite" timeline events, and will also be used for other things soon. WebKit2 clients can call these via the same-named functions on WebPage. These need hooking up for Coordinated Graphics, at the DrawingArea level.
Pull request: https://github.com/WebKit/WebKit/pull/18543
Committed 268770@main (fe9dc550d9a0): <https://commits.webkit.org/268770@main> Reviewed commits have been landed. Closing PR #18543 and removing active labels.