When error bubble gets added to CodeMirror it's whole layout seems to be mislayouted as if nothing was added to its DOM.
Created attachment 192449 [details] Patch
Comment on attachment 192449 [details] Patch You missed one return in the middle.
Created attachment 192485 [details] Patch
I slightly modified the order of operations - now it should look good.
Comment on attachment 192485 [details] Patch Clearing flags on attachment: 192485 Committed r145723: <http://trac.webkit.org/changeset/145723>
All reviewed patches have been landed. Closing bug.