(overlays-in (point-min) (point-max)) returns what you would expect:
#<overlay from 397 to 400 in *scratch*>
This was with a slightly altered example, I removed the overly long comment as it took forever to draw. 100% cpu resources are used when the line is being drawn, and it seems to be redrawn many times before it's finally done. Then all is well until something causes the line to be redrawn.
I'm not sure what 'RSS' means in this context, but I assumed you wanted a screenshot of top:
Unfortunately emacs isn't shown here, but X always takes the blame for the resource use, never emacs. I have tried interrupting whatever is going on with C-g after toggling debug-on-error, but I'm unable to interrupt anything in this manner.
FWIW I cannot reproduce this bug on any other computers either. My desktop computer runs an almost identical software stack but is unaffected.
I will try to attach a debugger, but my computer is quite unusable after triggering this problem, so it may be difficult.