The old multi-column code could at least handle nested columns as an unsplittable unit. The new code should do the same. Right now it is dropping them completely, which will undoubtedly cause regressions in children's books in iBooks.
This is a blocker for turning the new columns on.
This is the challenging one. I wish I knew if iBooks depends on this or not.
Created attachment 229923 [details]
Work in progress. Everything working now except for transparency. I need to patch bounding box for that to know how to recur.
Created attachment 229935 [details]
Attachment 229935 [details] did not pass style-queue:
ERROR: Source/WebCore/rendering/RenderLayer.h:714: Weird number of spaces at line-start. Are you using a 4-space indent? [whitespace/indent] 
ERROR: Source/WebCore/rendering/RenderLayer.cpp:4312: When wrapping a line, only indent 4 spaces. [whitespace/indent] 
Total errors found: 2 in 6 files
If any of these errors are false positives, please file a bug against check-webkit-style.
Created attachment 229945 [details]
Fixed in r167714.