net, tls, http: remove socket.ondrain

Replace the ondrain hack with a regular 'drain' listener. Speeds up the
bytes/1024 http benchmark by about 1.2%.

lib/http.js

@@ -1406,13 +1406,15 @@ exports.get = function(options, cb) {
   return req;
 };
 
+
+function ondrain() {
+  if (this._httpMessage) this._httpMessage.emit('drain');
+}
+
+
 function httpSocketSetup(socket) {
-  // NOTE: be sure not to use ondrain elsewhere in this file!
-  socket.ondrain = function() {
-    if (socket._httpMessage) {
-      socket._httpMessage.emit('drain');
-    }
-  };
+  socket.removeListener('drain', ondrain);
+  socket.on('drain', ondrain);
 }
 
 

lib/net.js

@@ -516,8 +516,6 @@ function afterWrite(status, handle, req, buffer) {
   self._pendingWriteReqs--;
 
   if (self._pendingWriteReqs == 0) {
-    // TODO remove all uses of ondrain - this is not a good hack.
-    if (self.ondrain) self.ondrain();
     self.emit('drain');
   }
 

lib/tls.js

@@ -461,9 +461,6 @@ CryptoStream.prototype._pull = function() {
       debug('drain ' + (this === this.pair.cleartext ? 'clear' : 'encrypted'));
       var self = this;
       process.nextTick(function() {
-        if (typeof self.ondrain === 'function') {
-          self.ondrain();
-        }
         self.emit('drain');
       });
       this._needDrain = false;