1. @DomName('WebGL2RenderingContext.stencilMaskSeparate')
  2. @DocsEditable()
  3. @Experimental()
void stencilMaskSeparate(int face, int mask)

Source 

@DomName('WebGL2RenderingContext.stencilMaskSeparate')
@DocsEditable()
@Experimental() // untriaged
void stencilMaskSeparate(int face, int mask) =>
    _blink.BlinkWebGL2RenderingContext.instance
        .stencilMaskSeparate_Callback_2_(this, face, mask);