The TileController root layer gets parented both directly and as a "custom" sublayer of its owning layer. We don't need to parent it directly, only the custom sublayer mechanism was intended to be used (so that they'll stay put in the layer hierarchy).
Created attachment 217850 [details] patch
Comment on attachment 217850 [details] patch r=me. Parenting yourself is gross! Gross I say!
Comment on attachment 217850 [details] patch Clearing flags on attachment: 217850 Committed r159800: <http://trac.webkit.org/changeset/159800>
All reviewed patches have been landed. Closing bug.