layout() {
        if (this.orientation === 0 /* Orientation.VERTICAL */) {
            const verticalProvider = this.layoutProvider;
            this.el.style.left = verticalProvider.getVerticalSashLeft(this) - (this.size / 2) + 'px';
            if (verticalProvider.getVerticalSashTop) {
                this.el.style.top = verticalProvider.getVerticalSashTop(this) + 'px';
            }
            if (verticalProvider.getVerticalSashHeight) {
                this.el.style.height = verticalProvider.getVerticalSashHeight(this) + 'px';
            }
        }
        else {
            const horizontalProvider = this.layoutProvider;
            this.el.style.top = horizontalProvider.getHorizontalSashTop(this) - (this.size / 2) + 'px';
            if (horizontalProvider.getHorizontalSashLeft) {
                this.el.style.left = horizontalProvider.getHorizontalSashLeft(this) + 'px';
            }
            if (horizontalProvider.getHorizontalSashWidth) {
                this.el.style.width = horizontalProvider.getHorizontalSashWidth(this) + 'px';
            }
        }
    }
Layout the sash. The sash will size and position itself
based on its provided {@link ISashLayoutProvider layout provider}.