RoundedCornerTreatment.m

- (MDCPathGenerator *)pathGeneratorForCornerWithAngle:(CGFloat)angle 
                                            andRadius:(CGFloat)radius {
  MDCPathGenerator *path =
      [MDCPathGenerator pathGeneratorWithStartPoint:CGPointMake(0, radius)];
  [path addArcWithTangentPoint:CGPointZero
                       toPoint:CGPointMake(MDCSin(angle) * radius, MDCCos(angle) * radius)
                        radius:radius];
  return path;
}