It wasn't gamesmanship. Plenty of players move around like that before the serve. I've seen Maria and Ana both do it. Sharapova should have realized that Aga was moving backwards once she actually served not to mention her returns were hardly overpowering.
Golovin-Dementieva-Likhovtseva-Beltrame-Benešová-Chakvetadze-Szávay-Paszek-Cirstea Vera Zvonareva Riding the 3AM Rollercoaster