Remove NOTIMPLEMENTED in UnixDomainServerSocket.

GetLocalAddress should return ERR_SOCKET_ADDRESS_INVALID, as it
does for UnixDomainClientSocket.

This cleans up another piece of logspam.

BUG=431412

Review URL: https://codereview.chromium.org/1216243006

Cr-Commit-Position: refs/heads/master@{#337374}
diff --git a/net/socket/unix_domain_server_socket_posix.cc b/net/socket/unix_domain_server_socket_posix.cc
index 6866d36..ee327ac0 100644
--- a/net/socket/unix_domain_server_socket_posix.cc
+++ b/net/socket/unix_domain_server_socket_posix.cc
@@ -103,8 +103,11 @@
 }
 
 int UnixDomainServerSocket::GetLocalAddress(IPEndPoint* address) const {
-  NOTIMPLEMENTED();
-  return ERR_NOT_IMPLEMENTED;
+  DCHECK(address);
+
+  // Unix domain sockets have no valid associated addr/port;
+  // return address invalid.
+  return ERR_ADDRESS_INVALID;
 }
 
 int UnixDomainServerSocket::Accept(scoped_ptr<StreamSocket>* socket,