GPU 3D transforms: every container renders on the device

3D and perspective transforms move to the GPU, completing the set of container primitives. A tilted, perspective-projected element renders its content to a GPU layer, and each screen pixel is gathered back through the inverse perspective with four subsamples for smooth edges - the same anti-aliased projection the software renderer does, within two levels. With this, every wrapper the renderer understands - rounded clips, 2D and 3D transforms, and all ten CSS filters - runs on the device, on top of the full 2D paint set. That is the whole 2D-and-effects pipeline on the GPU. The GPU aspect moves 44 to 46. What is left is turning this into the default live render path, plus WebGL and video decode. The overall holds at 57.