For the last few days I have been trying ti install the Native Client SDK for chrome in Windows and/or Ubuntu.
I'm behind a corporate network, and the only internet access is through an HTTP proxy with authentication involved.
When I run "naclsdk update" in Ubuntu, it shows 
"urlopen error Tunnel connection failed: 407 Proxy Authentication Required"
Can anyone please help ?
I got a solution-
not a direct one, though.
 managed to use a program to redirect the HTTPS traffic through the HTTP proxy.
I used the program called "proxifier". Works great.
Installing Chrome Native Client SDK