Bug 161450 uncovered this. The style checker flags Objective C blocks as invalid syntax when they are passed as an argument to an Objective C function.
Created attachment 289601 [details]
Comment on attachment 289601 [details]
Clearing flags on attachment: 289601
Committed r206911: <http://trac.webkit.org/changeset/206911>
All reviewed patches have been landed. Closing bug.