Add CHECK() in UdpSocketLibevent to debug crbug.com/452121

content/browser/renderer_host/p2p/socket_host_udp_unittest.cc

Index: content/browser/renderer_host/p2p/socket_host_udp_unittest.cc
diff --git a/content/browser/renderer_host/p2p/socket_host_udp_unittest.cc b/content/browser/renderer_host/p2p/socket_host_udp_unittest.cc
index 5d67a24fc3327563c21773cc973ae8ba7084e7b0..c4200cb2e48e52ec08166b30af334faf73bf8acb 100644
--- a/content/browser/renderer_host/p2p/socket_host_udp_unittest.cc
+++ b/content/browser/renderer_host/p2p/socket_host_udp_unittest.cc
@@ -46,7 +46,7 @@ class FakeDatagramServerSocket : public net::DatagramServerSocket {
       : sent_packets_(sent_packets) {
   }
 
-  void Close() override {}
+  int Close() override { return net::OK; }
 
   int GetPeerAddress(net::IPEndPoint* address) const override {
     NOTREACHED();