The world’s largest retailer, Walmart, plans to introduce an inexpensive, kid-friendly tablet computer under its ONN store brand. The device will be made by a Chinese supplier and run on Google’s Android operating system. The price of the device, or when it will be launch, hasn’t been disclosed. The tablet market has been growing at a sluggish pace since tablet users don’t buy new ones at the same pace as they replace smartphones. Apple Inc.’s iPad brand is the top-selling tablet brand.