This thing is essentially a wrapper around an SkPath, although we do
some indirection via a PathImpl class to keep the door open for
alternative rasterizer/path backends in the future.
We also update the 2D canvas code, since that was the only code that
used Painter+DeprecatedPath, and this allows us to just drop that
code instead of temporarily supporting it until the next commit.
The transform can change between path building operations (and before
the path is filled or stroked). This fixes the sun ray backgroun on
the https://www.kevs3d.co.uk/dev/html5logo/ canvas demo.
