Change tessellator sweep direction to depend on path aspect ratio.

The tessellating path renderer uses several sweep-line algorithms,
whose sweep direction can be either in X or Y.

It is currently set to in-X at compile time, but a better approach is to
make it runtime-configurable, and use the path aspect ratio as
a heuristic to determine the optimal sweep direction.

BUG=skia:3725

Review URL: https://codereview.chromium.org/1089073002
1 file changed