Currently Scene.toImage() and Picture.toImage() return the image asynchronously through 'makeSnapshot'. Ideally, these would call a GPU specific version of 'makeSnapshot' and return the result synchronously so the result can be used in further drawing on the same frame.

This opens up the door for numerous effects, but can also be incorporated into 'paintImage' in conjunction with ImageShader to help speed up image tiling which currently issues a draw command for each tile.

See here for more information:
flutter/engine#8835 (comment)

cc @Hixie @liyuqian @reed-at-google