src/vs/workbench/api/browser/mainThreadDocuments.ts/ModelTracker/constructor
class ModelTracker:	constructor(
		private readonly _model: ITextModel,
		private readonly _onIsCaughtUpWithContentChanges: Emitter<URI>,
		private readonly _proxy: ExtHostDocumentsShape,
		private readonly _textFileService: ITextFileService,
	) {
		super();
		this._knownVersionId = this._model.getVersionId();
		this._register(this._model.onDidChangeContent((e) => {
			this._knownVersionId = e.versionId;
			this._proxy.$acceptModelChanged(this._model.uri, e, this._textFileService.isDirty(this._model.uri));
			if (this.isCaughtUpWithContentChanges()) {
				this._onIsCaughtUpWithContentChanges.fire(this._model.uri);
			}
		}));
	}