src/vs/base/browser/ui/splitview/paneview.ts/Pane/layout
class Pane:	layout(size: number): void {
		const headerSize = this.headerVisible ? Pane.HEADER_SIZE : 0;

		const width = this._orientation === Orientation.VERTICAL ? this.orthogonalSize : size;
		const height = this._orientation === Orientation.VERTICAL ? size - headerSize : this.orthogonalSize - headerSize;

		if (this.isExpanded()) {
			this.body.classList.toggle('wide', width >= 600);
			this.layoutBody(height, width);
			this.expandedSize = size;
		}
	}