src/sksl/sksl_vert.include - skia - Git at Google

 STRINGIFY(

 // defines built-in interfaces supported by SkiaSL vertex shaders

 out gl_PerVertex {
   	layout(builtin=0) vec4 gl_Position;
   	layout(builtin=1) float gl_PointSize;
 };

 )
	STRINGIFY(

	// defines built-in interfaces supported by SkiaSL vertex shaders

	out gl_PerVertex {
	layout(builtin=0) vec4 gl_Position;
	layout(builtin=1) float gl_PointSize;
	};

	)