http://trac.webkit.org/changeset/109851/ regressed (or revealed) a bug in some compositing content (test case attached). The size of the #slider layer is not big enough to contain the transformed children.
Created attachment 140660 [details] Testcase
<rdar://problem/11401995>
<rdar://problem/11402771>
RenderLayer::calculateLayerBounds() is using convertToLayerCoords() which ignores transforms!
Ah, the actual bug was caused by http://trac.webkit.org/changeset/114518, by the newly added UseLocalClipRectIfPossible code path in RenderLayer::calculateLayerBounds() which didn't handle transforms.
Created attachment 140675 [details] Patch
Comment on attachment 140675 [details] Patch View in context: https://bugs.webkit.org/attachment.cgi?id=140675&action=review > Source/WebCore/rendering/RenderLayer.cpp:4163 > + TransformationMatrix* affineTrans = layer->transform(); Weird name for a local variable that’s not really needed.
http://trac.webkit.org/changeset/116395