src/vs/platform/layout/browser/zIndexRegistry.ts/ZIndexRegistry/updateStyleElement
class ZIndexRegistry:	private updateStyleElement(): void {
		clearNode(this.styleSheet);
		let ruleBuilder = '';
		this.zIndexMap.forEach((zIndex, name) => {
			ruleBuilder += `${this.getVarName(name)}: ${zIndex};\n`;
		});
		createCSSRule(':root', ruleBuilder, this.styleSheet);
	}