Expose SkBlender

[mattleibow]

Description of Change

Adds a new type SkBlender and usages of that type to the C API.

SkiaSharp Issue

Related to mono/SkiaSharp#2830

API Changes

// sk_blender_t
void sk_blender_ref(sk_blender_t* blender);
void sk_blender_unref(sk_blender_t* blender);
sk_blender_t* sk_blender_new_mode(sk_blendmode_t mode);
sk_blender_t* sk_blender_new_arithmetic(float k1, float k2, float k3, float k4, bool enforcePremul);

// sk_imagefilter_t
sk_imagefilter_t* sk_imagefilter_new_blender(sk_blender_t* blender, const sk_imagefilter_t* background, const sk_imagefilter_t* foreground, const sk_rect_t* cropRect);

// sk_paint_t
void sk_paint_set_blender(sk_paint_t* paint, sk_blender_t* blender);
sk_blender_t* sk_paint_get_blender(sk_paint_t* cpaint);

// sk_runtimeeffect_t
sk_runtimeeffect_t* sk_runtimeeffect_make_for_blender(sk_string_t* sksl, sk_string_t* error);
sk_blender_t* sk_runtimeeffect_make_blender(sk_runtimeeffect_t* effect, sk_data_t* uniforms, sk_flattenable_t** children, size_t childCount);

// sk_shader_t
sk_shader_t* sk_shader_new_blender(sk_blender_t* blender, const sk_shader_t* dst, const sk_shader_t* src);

Behavioral Changes

None.

Required SkiaSharp PR

Requires mono/SkiaSharp#2830

PR Checklist

• Rebased on top of skiasharp at time of PR
• Changes adhere to coding standard
• Updated documentation