Why, wonders Joe Weisenthal, are we only finding out about this now? The National Restaurant Association sought the measure — which constricts the freedom of its own membership — in hopes of gaining uniformity instead of “a potential patchwork of conflicting requirements adopted by states and cities,” to quote the Times. It can be reliably predicted, though, that the ever-growing battalions of “food policy advocates” will 
not feel constrained by any supposed national deal to refrain from pushing for further piecemeal extension of state and local requirements, thus rendering any seeming uniformity but temporary.
The requirement kicks in when a restaurant chain reaches ten units, and will foreseeably make it harder for 15-unit local chains to compete with the 1,500-unit behemoths who can spread the nontrivial costs of compliance over a much larger base. Like earlier calorie-labeling laws, it will also encourage standardization by making it hazardous for owners not to prescribe and control, e.g., precisely how much topping local employees are to spread on each sandwich or pizza. Earlier here. More: Richard Goldfarb at Food Liability Law Blog has more details, and reports that the threshold for number of outlets is 20 rather than 15. There also some pre-emption of state and local regulation, although localities can still impose added requirements in the name of food safety.