SVG and and CSS border rendering now sits on top of SkPath instead of
the old Gfx::DeprecatedPath.
Due to an imperceptible (255, 255, 255) vs (255, 254, 255) color diff
in one ref test, I changed that test to not depend on border rendering
for a positive result, since that was incidental.
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.
