src/vs/workbench/api/browser/mainThreadDocumentsAndEditors.ts/MainThreadDocumentAndEditorStateComputer/_updateStateOnModelAdd
class MainThreadDocumentAndEditorStateComputer:	private _updateStateOnModelAdd(model: ITextModel): void {
		if (!shouldSynchronizeModel(model)) {
			// ignore
			return;
		}

		if (!this._currentState) {
			// too early
			this._updateState();
			return;
		}

		// small (fast) delta
		this._currentState = new DocumentAndEditorState(
			this._currentState.documents.add(model),
			this._currentState.textEditors,
			this._currentState.activeEditor
		);

		this._onDidChangeState(new DocumentAndEditorStateDelta(
			[], [model],
			[], [],
			undefined, undefined
		));
	}