Robohornet's reflow test spends 2% of total time in recommendedScrollerStyle() http://www.robohornet.org/tests/offsetreflow.html An easy fix would be to cache the preferredScrollerStyle value and listen for the notification: https://developer.apple.com/library/mac/#documentation/Cocoa/Reference/ApplicationKit/Classes/NSScroller_Class/Reference/Reference.html#//apple_ref/occ/clm/NSScroller/preferredScrollerStyle Unclear how much (if at all) this affects real web content.
*** Bug 98623 has been marked as a duplicate of this bug. ***