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

net/socket/socket_test_util.cc

Index: net/socket/socket_test_util.cc
diff --git a/net/socket/socket_test_util.cc b/net/socket/socket_test_util.cc
index 791c9f684804dd7fd74ac8adee3b2a5e7d8cc164..1ec40afc5589053fcbc11cf74bdc1682097df0ec 100644
--- a/net/socket/socket_test_util.cc
+++ b/net/socket/socket_test_util.cc
@@ -1202,8 +1202,9 @@ int DeterministicMockUDPClientSocket::SetSendBufferSize(int32 size) {
   return OK;
 }
 
-void DeterministicMockUDPClientSocket::Close() {
+int DeterministicMockUDPClientSocket::Close() {
   connected_ = false;
+  return OK;
 }
 
 int DeterministicMockUDPClientSocket::GetPeerAddress(
@@ -1615,8 +1616,9 @@ int MockUDPClientSocket::SetSendBufferSize(int32 size) {
   return OK;
 }
 
-void MockUDPClientSocket::Close() {
+int MockUDPClientSocket::Close() {
   connected_ = false;
+  return OK;
 }
 
 int MockUDPClientSocket::GetPeerAddress(IPEndPoint* address) const {