src/vs/workbench/services/decorations/browser/decorationsService.ts/DecorationRule/appendCSSRules
class DecorationRule:	appendCSSRules(element: HTMLStyleElement, theme: IColorTheme): void {
		if (!Array.isArray(this.data)) {
			this._appendForOne(this.data, element, theme);
		} else {
			this._appendForMany(this.data, element, theme);
		}
	}