src/vs/base/browser/ui/grid/gridview.ts/BranchNode/setChildVisible
class BranchNode:	setChildVisible(index: number, visible: boolean): void {
		index = validateIndex(index, this.children.length);

		if (this.splitview.isViewVisible(index) === visible) {
			return;
		}

		this.splitview.setViewVisible(index, visible);
	}