Improve the curve tessellation subdivision of the path renderers.
The stencil-and-cover and tessellating path renderers currently
tessellate curves to linear segments to within one screen space pixel.
This is fairly poor accuracy, as can be seen from the strokecircle GM:
there are noticeable rotating bumps on the circles.
Improving the tolerance to 0.25 pixel eliminates the bumps, and
approximates the 16x supersampling of the raster path.
This does have a performance hit: 3-6% on desktop on
the IE chalkboard demo, ~1% on Nexus 7 2013.
Note: this will require rebaselining a number of GPU and MSAA images
in Skia, but nothing in Chrome (yet).
BUG=skia:3731
Review URL: https://codereview.chromium.org/1072273007
3 files changed