The assert: document->cssRegionsEnabled() is specific to CSSRegions feature and should not be used for multicolumn (requested by David Hyatt in https://bugs.webkit.org/show_bug.cgi?id=113658#c5)
Created attachment 196300 [details] Patch
Comment on attachment 196300 [details] Patch Clearing flags on attachment: 196300 Committed r147531: <http://trac.webkit.org/changeset/147531>
All reviewed patches have been landed. Closing bug.