Add a SetDoNotFragment() method to DatagramSocket, and call this for

jingle/glue/proxy_resolving_client_socket.h

Index: jingle/glue/proxy_resolving_client_socket.h
diff --git a/jingle/glue/proxy_resolving_client_socket.h b/jingle/glue/proxy_resolving_client_socket.h
index 9777ef776ee49ad9d213a31e362734e2839e0168..845ad339146dd0cbb2555a4765ca6282b97a1d6f 100644
--- a/jingle/glue/proxy_resolving_client_socket.h
+++ b/jingle/glue/proxy_resolving_client_socket.h
@@ -61,6 +61,7 @@ class ProxyResolvingClientSocket : public net::StreamSocket {
             const net::CompletionCallback& callback) override;
   int SetReceiveBufferSize(int32_t size) override;
   int SetSendBufferSize(int32_t size) override;
+  int SetDoNotFragment(bool do_not_fragment) override;
   int Connect(const net::CompletionCallback& callback) override;
   void Disconnect() override;
   bool IsConnected() const override;