The timeline is a fantastic addition to web inspector. One thing that'd make it even more useful for me is to have screen snapshots for each paint event. Currently it's hard for me to tell if a "paint" just painted one pixel, the top banner, or the entire page. I do get a paint dimensions but it's not always obvious what was within those dimensions at the time of the paint event. Having a low-res snapshot that shows the entire page as well as the changed region (for instance, gray out/fade the entire page, and show the newly painted region without being faded) in order to understand what the whole page looks like as well as what changed during that paint event would be a great addition to this tool.
Sounds like we had a bug for it, merging in. *** This bug has been marked as a duplicate of bug 46340 ***