Use SkSL to do point-light shading

- misc fixes to utilities
- hit-testing for 3D scenes (simple version)

Had to manually inform the shader of the local-to-world matrix.
Should try making that automatic in the future.

Note: due to bug in interpreter, point-light sample can't run in raster

Change-Id: I7a30b7676ea6cd7eb264373dd2507133c901d85e
Reviewed-by: Mike Reed <>
Commit-Queue: Mike Reed <>
5 files changed