src/vs/workbench/common/editor/editorGroupModel.ts/EditorGroupModel/setGroupActive
class EditorGroupModel:	private setGroupActive(): void {
		// We do not really keep the `active` state in our model because
		// it has no special meaning to us here. But for consistency
		// we emit a `onDidModelChange` event so that components can
		// react.
		this._onDidModelChange.fire({ kind: GroupModelChangeKind.GROUP_ACTIVE });
	}