src/vs/workbench/services/editor/browser/editorService.ts/EditorService/registerGroupListeners
class EditorService:	private registerGroupListeners(group: IEditorGroupView): void {
		const groupDisposables = new DisposableStore();

		groupDisposables.add(group.onDidGroupChange(e => {
			if (e.kind === GroupChangeKind.EDITOR_ACTIVE) {
				this.handleActiveEditorChange(group);
				this._onDidVisibleEditorsChange.fire();
			}
		}));

		groupDisposables.add(group.onDidCloseEditor(event => {
			this._onDidCloseEditor.fire(event);
		}));

		groupDisposables.add(group.onDidOpenEditorFail(editor => {
			this._onDidOpenEditorFail.fire({ editor, groupId: group.id });
		}));

		Event.once(group.onWillDispose)(() => {
			dispose(groupDisposables);
		});
	}