Quoting Nat: Can we make it part of rendering, e.g. purple? Its part of webkit's stuff, whereas green is mainly the painting system. I just was tuning kix and was thinking for the longest time that it was bottlenecked on painting, but in reality, it was bottlenecked on having a slow scroll handler.
Created attachment 195712 [details] Patch
Committed r147208: <http://trac.webkit.org/changeset/147208>