Function radial_gradient_pattern 

pub fn radial_gradient_pattern(
    center: LayoutPoint,
    scale: DeviceVector2D,
    start_radius: f32,
    end_radius: f32,
    ratio_xy: f32,
    extend_mode: ExtendMode,
    stops: &[GradientStop],
    _is_software: bool,
    gpu_buffer_builder: &mut GpuBufferBuilder,
) -> Pattern