Where was the American video game developer which has Demonware as a subsidiary headquartered? 
Demonware: Demonware is an Irish software development company and a subsidiary of Activision Blizzard. Activision Blizzard:  Headquartered in Santa Monica, California and founded in 2008 through the merger of Vivendi Games and Activision, the company is traded on the NASDAQ stock exchange under the ticker symbol NASDAQ: ATVI , and since 2015 has been one of the stocks that make up the S&P 500.
Santa Monica, California