Cleanup the getting and setting of the socket file descriptor

runtime/bin/socket.h

Index: runtime/bin/socket.h
diff --git a/runtime/bin/socket.h b/runtime/bin/socket.h
index 3e5c40c153cc08815b564ede373410e85cd8ef1d..1bec3e61d5b7af3e2d5a999d8dc1661f011aafda 100644
--- a/runtime/bin/socket.h
+++ b/runtime/bin/socket.h
@@ -202,8 +202,8 @@ class Socket {
 
   static Dart_Port GetServicePort();
 
-  static Dart_Handle SetSocketIdNativeField(Dart_Handle socket, intptr_t id);
-  static Dart_Handle GetSocketIdNativeField(Dart_Handle socket, intptr_t* id);
+  static void SetSocketIdNativeField(Dart_Handle socket, intptr_t id);
+  static intptr_t GetSocketIdNativeField(Dart_Handle socket);
 
  private:
   static dart::Mutex* mutex_;