UserAgent: Mozilla/5.0 (Windows NT 10.0; WOW64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/56.0.2924.87 Safari/537.36

Steps to reproduce the problem:
There are certain HTTP/HTTPS Proxy server that check the HTTP User-Agent header field, for example to only allow defined Browsers.
Chrome does not include the User-Agent field when sending a CONNECT request to a HTTP proxy to establish a connection to a turn server. I'm able to reproduce this by:

1. Setting up a HTTP proxy that requires user agent header
2. Setting up a Win client machise with network access only to the machine hosting the  proxy
3. Setting the HTTP and HTTPS proxies in Windows's Network configuration
4. Opening chrome
5. Placing a webrtc call

What is the expected behavior?
Chrome should successfully connect through the proxy and jingle should be able to communicate with the TURN server through the proxy....the chrome user-agent id should be transmitted in the user-agent header

What went wrong?
No user-agent header is transmitted.

Same Problem existed for Proxy Authentication Credentials. But therefore there is already a filed Bug and a Solution available for Canary.
https://bugs.chromium.org/p/chromium/issues/detail?id=439560

Did this work before? No 

Does this work in other browsers? N/A

Chrome version: 56.0.2924.87  Channel: stable
OS Version: 10.0
Flash Version: Shockwave Flash 24.0 r0

In large corporate networks it is quite common that proxy servers check the user-agent header. For webrtc to work correctly in those environments, the User-Agent header which is configured for Chrome and used in normal web request should be also transmitted in the webrtc turn requests.