They are closer to being boxes (rectangles sitting on the line) than being runs. Also the term 'run' is way overloaded.
Created attachment 438980 [details]
Created attachment 438983 [details]
Created attachment 439040 [details]
Tools/Scripts/svn-apply failed to apply attachment 439040 [details] to trunk.
Please resolve the conflicts and upload a new patch.
Created attachment 439041 [details]
Committed r282961 (242051@main): <https://commits.webkit.org/242051@main>
All reviewed patches have been landed. Closing bug and clearing flags on attachment 439041 [details].