src/vs/base/browser/ui/grid/gridview.ts/GridView/getViewCachedVisibleSize
class GridView:	getViewCachedVisibleSize(location: GridLocation): number | undefined {
		const [rest, index] = tail(location);
		const [, parent] = this.getNode(rest);

		if (!(parent instanceof BranchNode)) {
			throw new Error('Invalid location');
		}

		return parent.getChildCachedVisibleSize(index);
	}