Move UnixDomainSocket to base namespace

sandbox/linux/syscall_broker/broker_process_unittest.cc

Index: sandbox/linux/syscall_broker/broker_process_unittest.cc
diff --git a/sandbox/linux/syscall_broker/broker_process_unittest.cc b/sandbox/linux/syscall_broker/broker_process_unittest.cc
index bd7ef27aa49a5c85c27ac899d07e2a88236c0879..9ad0e719de22eca0879c48bf5f9475c4723255b7 100644
--- a/sandbox/linux/syscall_broker/broker_process_unittest.cc
+++ b/sandbox/linux/syscall_broker/broker_process_unittest.cc
@@ -541,7 +541,7 @@ SANDBOX_TEST_ALLOW_NOISE(BrokerProcess, RecvMsgDescriptorLeak) {
   // available, but for good measure we send it fd_limit bogus IPCs anyway.
   for (rlim_t i = 0; i < fd_limit; ++i) {
     SANDBOX_ASSERT(
-        UnixDomainSocket::SendMsg(ipc_fd, kBogus, sizeof(kBogus), fds));
+        base::UnixDomainSocket::SendMsg(ipc_fd, kBogus, sizeof(kBogus), fds));
   }
 
   const int fd = open_broker.Open(kCpuInfo, O_RDONLY);