Right now any overflow region with overlay scrollbars will cause a second pass through the layer tree to paint said scrollbars. Except right now both passes end up painting custom css scrollbars. Patch forthcoming. <rdar://problem/9389072>
Created attachment 92665 [details] Patch
This test doesn't do anything right now, but when we have a version of DRT that uses overlay scrollbars, then this test will be valuable.
Comment on attachment 92665 [details] Patch View in context: https://bugs.webkit.org/attachment.cgi?id=92665&action=review > Source/WebCore/rendering/RenderLayer.cpp:2254 > + // If this is the special overlay scrollbar painting pass, then don't re-paint any > + // non-overlay scrollbars. Only custom-CSS scrollbars will be non-overlay in this > + // context. This comment seems a little long. Maybe you could remove more of what's redundant with the code and concentrate on the why part of this?
(In reply to comment #3) > (From update of attachment 92665 [details]) > View in context: https://bugs.webkit.org/attachment.cgi?id=92665&action=review > > > Source/WebCore/rendering/RenderLayer.cpp:2254 > > + // If this is the special overlay scrollbar painting pass, then don't re-paint any > > + // non-overlay scrollbars. Only custom-CSS scrollbars will be non-overlay in this > > + // context. > > This comment seems a little long. Maybe you could remove more of what's redundant with the code and concentrate on the why part of this? Thanks Darin! I changed it to a better, more-concise comment. Committed with revision 85990.