Remove WrapPreserve3DList() and replaced it by creating a
nsDisplayTransform item for each transformed frame.
- Add an additional item for each top frame extending 3D context to
separate consequence contexts.
- Effective transform of a layer is the accumulation of ancestors in
the same 3D context.
- The layers creating new context and extended by children need a
temporary buffer if it's effective transform is not 2D.
- Clip rects are accumulated along the context chain.
- Visible rects of items are computed from dirty regions of the frame
creating the context and accumulated transforms.
- Bounds of items are computed from accumulated transforms and
accumulated bounds of the descent frames.
- Backface hidden is handled by compositor and BasicLayerManager.
c4820d6fca