src/vs/editor/contrib/documentSymbols/browser/outlineModel.ts/OutlineModelService/constructor
class OutlineModelService:	constructor(
		@ILanguageFeaturesService private readonly _languageFeaturesService: ILanguageFeaturesService,
		@ILanguageFeatureDebounceService debounces: ILanguageFeatureDebounceService,
		@IModelService modelService: IModelService
	) {
		this._debounceInformation = debounces.for(_languageFeaturesService.documentSymbolProvider, 'DocumentSymbols', { min: 350 });

		// don't cache outline models longer than their text model
		this._disposables.add(modelService.onModelRemoved(textModel => {
			this._cache.delete(textModel.id);
		}));
	}