unable to Disable WebRTC

Hello.
How can i disable WebRTC in Chrome, i used some extensions in chrome at first they disable then after few minutes they fail to disable it. Can you guys help me and tell me which is the best tool to disable WebRTC. And how can i disable timezone in chrome browser while using proxy. I am using proxy/vpn to disable my location but when i run a test on doileak and other websites its displaying my real time zone and also the proxy locations time zone.

this help ? http://www.slimjet.com/en/how-to-disable-webrtc-in-chrome.php