Run this code in the console: wm = new WeakMap wm.set(wm, wm)
Good find!
In may case, the console is not hanging. It just didn't output anything for the object. You can continue to use the console. What actually happened is the backend generated an "error" trying to generate the RemoteObject for the object (specifically the preview). That said, this still stinks. I have a fix, that gets this working, and fixes a few other possible subtle issues (propagating lossless to the top).
Created attachment 258923 [details] [PATCH] Proposed Fix
Created attachment 258924 [details] [IMAGE] After - Cyclic Set
Created attachment 258925 [details] [IMAGE] After - Cyclic Map
Comment on attachment 258923 [details] [PATCH] Proposed Fix Clearing flags on attachment: 258923 Committed r188403: <http://trac.webkit.org/changeset/188403>
All reviewed patches have been landed. Closing bug.
<rdar://problem/22276141>