Chris Brown lends a hand on “Drop It Low,” the debut single from Ester Dean out of Polow Da Don’s Zone 4 Inc. camp. The singer-songwriter has worked with everyone from Keyshia Cole and Keri Hilson to the Pussycat Dolls and Mary J. Blige (“Stronger”). The Polow production can be found on the soundtrack to More Than a Game (Sept. 22). Now if we could only find a photo of Ester…