Stub out new classes to represent the region boxes for columns.
Created attachment 132653 [details]
Attachment 132653 [details] did not pass style-queue:
Failed to run "['Tools/Scripts/check-webkit-style', '--diff-files', u'Source/WebCore/ChangeLog', u'Source/WebCor..." exit_code: 1
Source/WebCore/rendering/RenderRegionSet.h:31: Alphabetical sorting problem. [build/include_order] 
Total errors found: 1 in 10 files
If any of these errors are false positives, please file a bug against check-webkit-style.
Comment on attachment 132653 [details]
View in context: https://bugs.webkit.org/attachment.cgi?id=132653&action=review
> +// object, we significantly reduce the # of unique RenderObjects required to represent columns.
Spell out “number”?
> +// By combining runs of same-size columns or pages into a single object, we significantly reduce the # of unique RenderObjects
Fix landed in r111240.