Sony Corp , widely regarded as a key supplier of image sensors for Apple Inc’s (AAPL.O) iPhones, said on Friday it was bracing for a slowdown in the premium smartphone market after sales of its sensors fell in the third quarter. Videogame sales and cost cuts in Sony’s flagging mobile unit pushed October-December operating profit up 11 percent, beating analyst estimates, but the firm confirmed a much-feared hit to a segment that in recent quarters helped it shake off years of losses.