When RenderLayers become compositing because of a 3d transform or a transition, they sometimes jump around incorrectly. This happens when some other element with backing projects above/to the left of the document.
Created attachment 31332 [details] Testcase
The bug is that in rebuildCompositingLayerTree() the answer to calculateCompositedBounds() changes as later siblings become composited.
<rdar://problem/6944442>
Created attachment 31680 [details] Patch, testcase, changelog
Comment on attachment 31680 [details] Patch, testcase, changelog r=me
http://trac.webkit.org/changeset/44961
*** Bug 27272 has been marked as a duplicate of this bug. ***