LONDON, Sept 22 (Reuters) - David Luiz has pledged his future to Chelsea by signing a new five-year deal and manager Roberto Di Matteo is confident contract negotiations with Ashley Cole will also reach a successful conclusion. Both players featured in Saturday's 1-0 home victory over Stoke City in the Premier League, left back Cole highlighting his importance to the European champions by popping up with the late winner. "I am very happy to sign a new contract," Brazil centre back David Luiz told the club's website (www.chelseafc.com). ... More...