Filter virtual network interfaces for p2p sessions.

For WebRTC virtual host scoped network interfaces are not useful, but if present they take processing time and webrtc applications keep sending STUN ping messages from virtual network interfaces. 

This CL adding a policy for net::GetNetworkList method, which allows users of the method to include or exclude these interfaces.

R=agl@chromium.org,sergeyu@chromium.org
TBR=bbudge@chromium.org,ananta@chromium.org

Review URL: https://codereview.chromium.org/99133020

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@241830 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 241830