Clicking a <button> (which has a user agent rule of -webkit-user-select: ignore) clears the selection in contenteditable areas. This makes it impossible to create a editing toolbar.
Note that non-editable selections aren't cleared in the document.
Created attachment 14797 [details]
This is a regression I believe from when this first went in to open source...
I'll take this one.
Fixed in r24334 and r24336