Fix WebRTC IP leaks.

WebRTC binds to individual NICs and listens for incoming Stun packets. Sending stun through this specific NIC binding could make OS route the packet differently hence exposing non-VPN public IP.

The fix here is
1. to bind to any address (0:0:0:0) instead. This way, the routing will be the same as how chrome/http is.
2. also, remove the any all 0s addresses which happens when we bind to all 0s.




Review URL:

Cr-Commit-Position: refs/heads/master@{#8420}
git-svn-id: 4adac7df-926f-26a2-2b94-8c16560cd09d
diff --git a/webrtc/base/network.h b/webrtc/base/network.h
index 36aa5f8..089d86b 100644
--- a/webrtc/base/network.h
+++ b/webrtc/base/network.h
@@ -83,7 +83,8 @@
   // IP address.  (i.e. INADDR_ANY for IPv4 or in6addr_any for IPv6). This is
   // useful as binding to such interfaces allow default routing behavior like
   // http traffic.
-  virtual void GetAnyAddressNetworks(NetworkList* networks) = 0;
+  // TODO(guoweis): remove this body when chromium implements this.
+  virtual void GetAnyAddressNetworks(NetworkList* networks) {}
   // Dumps a list of networks available to LS_INFO.
   virtual void DumpNetworks(bool include_ignored) {}