src/vs/editor/browser/editorDom.ts/DynamicCssRules/garbageCollect
class DynamicCssRules:	private garbageCollect() {
		for (const rule of this._rules.values()) {
			if (!rule.hasReferences()) {
				this._rules.delete(rule.key);
				rule.dispose();
			}
		}
	}