recording the damage when we reflow the floater. This allows us to catch several cases that we weren't catching before, so we no longer need to dirty all the line boxes when an incremental reflow targeted at a float arrives. r=dbaron, sr=attinasi. git-svn-id: svn://10.0.0.236/trunk@119985 18797224-902f-48f8-a5cc-f745e15eee43