Also do ondrain callback for socket (needed by http)

lib/net.js

@@ -57,12 +57,16 @@ var ioWatchers = new FreeList("iowatcher", 100, function () {
 
 IOWatcher.prototype.ondrain = function () {
   assert(this.socket);
-  if (this.writable || this.readable) {
-    require('timers').active(this.socket);
-    this.socket.emit('drain');
+  var socket = this.socket;
+
+  if (socket.writable || socket.readable) {
+    require('timers').active(socket);
   }
 
-  if (this.socket._eof) this.socket._shutdown();
+  socket.emit('drain');
+  if (socket.ondrain) socket.ondrain();
+
+  if (socket._eof) socket._shutdown();
 };