src/vs/base/browser/ui/splitview/paneview.ts/Pane/maximumSize
class Pane:	get maximumSize(): number {
		const headerSize = this.headerSize;
		const expanded = !this.headerVisible || this.isExpanded();
		const maximumBodySize = expanded ? this.maximumBodySize : 0;

		return headerSize + maximumBodySize;
	}