make SetReceiveBufferSize and SetSendBufferSize return net error codes (instead of bools)

net/udp/udp_socket_libevent.cc

Index: net/udp/udp_socket_libevent.cc
diff --git a/net/udp/udp_socket_libevent.cc b/net/udp/udp_socket_libevent.cc
index 564627631a823b8e6c5efd7c9885e789aa056603..43ab1d46c4402967ea6f4f61a2dc45e62789d001 100644
--- a/net/udp/udp_socket_libevent.cc
+++ b/net/udp/udp_socket_libevent.cc
@@ -315,20 +315,22 @@ int UDPSocketLibevent::Bind(const IPEndPoint& address) {
   return rv;
 }
 
-bool UDPSocketLibevent::SetReceiveBufferSize(int32 size) {
+int UDPSocketLibevent::SetReceiveBufferSize(int32 size) {
   DCHECK(CalledOnValidThread());
   int rv = setsockopt(socket_, SOL_SOCKET, SO_RCVBUF,
                       reinterpret_cast<const char*>(&size), sizeof(size));
-  DCHECK(!rv) << "Could not set socket receive buffer size: " << errno;
-  return rv == 0;
+  int last_error = errno;
+  DCHECK(!rv) << "Could not set socket receive buffer size: " << last_error;
+  return MapSystemError(last_error);

[wtc, 2014/03/29 13:30:12]

This should be:
    return rv == 0 ? OK : MapSystemError(last_error);

The reason is that the value of errno is only trustworthy when a function fails.
A function is not required to set errno to 0 when it succeeds, so errno may
contain a stale error from a previous failed function call.

[jar (doing other things), 2014/04/01 23:50:39]

Done.

 }
 
-bool UDPSocketLibevent::SetSendBufferSize(int32 size) {
+int UDPSocketLibevent::SetSendBufferSize(int32 size) {
   DCHECK(CalledOnValidThread());
   int rv = setsockopt(socket_, SOL_SOCKET, SO_SNDBUF,
                       reinterpret_cast<const char*>(&size), sizeof(size));
-  DCHECK(!rv) << "Could not set socket send buffer size: " << errno;
-  return rv == 0;
+  int last_error = errno;
+  DCHECK(!rv) << "Could not set socket send buffer size: " << last_error;
+  return MapSystemError(last_error);

[wtc, 2014/03/29 13:30:12]

This should be: return rv == 0 ? OK : MapSystemError(last_error);

[jar (doing other things), 2014/04/01 23:50:39]

Done.

 }
 
 void UDPSocketLibevent::AllowAddressReuse() {