updateFillStyle(state, createFill) {
    const fillStyle = state.fillStyle;
    if (typeof fillStyle !== 'string' || state.currentFillStyle != fillStyle) {
      this.instructions.push(createFill.call(this, state));
      state.currentFillStyle = fillStyle;
    }
  }
@param {import("../canvas.js").FillStrokeState} state State.
@param {function(this:CanvasBuilder, import("../canvas.js").FillStrokeState):Array<*>} createFill Create fill.