src/vs/workbench/browser/parts/views/treeView.ts/TreeView/setVisibility
class TreeView:	setVisibility(isVisible: boolean): void {
		isVisible = !!isVisible;
		if (this.isVisible === isVisible) {
			return;
		}

		this.isVisible = isVisible;

		if (this.tree) {
			if (this.isVisible) {
				DOM.show(this.tree.getHTMLElement());
			} else {
				DOM.hide(this.tree.getHTMLElement()); // make sure the tree goes out of the tabindex world by hiding it
			}

			if (this.isVisible && this.elementsToRefresh.length) {
				this.doRefresh(this.elementsToRefresh);
				this.elementsToRefresh = [];
			}
		}

		this._onDidChangeVisibility.fire(this.isVisible);
	}