Added synchronous socket implementation to dart:io.

runtime/bin/socket_macos.cc

Index: runtime/bin/socket_macos.cc
diff --git a/runtime/bin/socket_macos.cc b/runtime/bin/socket_macos.cc
index b0990c44a8864aaba56b0dda082ab18aa5acf743..1f01ab315fce8c674718774433550b7434a837ca 100644
--- a/runtime/bin/socket_macos.cc
+++ b/runtime/bin/socket_macos.cc
@@ -7,20 +7,11 @@
 #include "platform/globals.h"
 #if defined(HOST_OS_MACOS)
 
+#include "bin/socket.h"
+
 #include <errno.h>        // NOLINT
-#include <ifaddrs.h>      // NOLINT
-#include <net/if.h>       // NOLINT
-#include <netinet/tcp.h>  // NOLINT
-#include <stdio.h>        // NOLINT
-#include <stdlib.h>       // NOLINT
-#include <string.h>       // NOLINT
-#include <sys/stat.h>     // NOLINT
-#include <unistd.h>       // NOLINT
 
 #include "bin/fdutils.h"
-#include "bin/file.h"
-#include "bin/socket.h"
-#include "bin/socket_base_macos.h"
 #include "platform/signal_blocker.h"
 
 namespace dart {