There is dire news coming out of the American retail industry these days. Malls that once teemed with eager shoppers are slowly dying, big-box stores are losing ground to e-commerce, and many legacy chains are shrinking their numbers in a too-little-too-late strategy to save themselves. Experts say it all points to a revolution that has been sparked by a sea change in consumer behavior, thanks to the ease of online shopping. The latest casualties are Toys R Us, which filed for bankruptcy in September and recently announced it will shutter all stores, and mall accessories chain Claire’s, which has also filed for bankruptcy. Wharton marketing professor Barbara Kahn and Mark Cohen, a former retail executive who is director of retail studies at Columbia University’s Graduate School of Business, joined the  Knowledge at Wharton show on SiriusXM channel 111 to talk about lessons from the downfall of Toys R Us and where the retail industry is headed.…