don't call DWM on Windows XP
don't call DWM on Windows XP

Fix rogerwang/node-webkit#1985

littlstar/chromium.src,littlstar/chromium.src,patrickm/chromium.src,ondra-novak/chromium.src,patrickm/chromium.src,littlstar/chromium.src,ondra-novak/chromium.src,ondra-novak/chromium.src,ondra-novak/chromium.src,patrickm/chromium.src,ondra-novak/chromium.src,patrickm/chromium.src,littlstar/chromium.src,ondra-novak/chromium.src,patrickm/chromium.src,littlstar/chromium.src,ondra-novak/chromium.src,patrickm/chromium.src,littlstar/chromium.src,patrickm/chromium.src,littlstar/chromium.src,patrickm/chromium.src,ondra-novak/chromium.src,ondra-novak/chromium.src,littlstar/chromium.src,patrickm/chromium.src