http: write buffers when chunked to embrace writev

lib/_http_outgoing.js

@@ -413,9 +413,15 @@ OutgoingMessage.prototype.write = function(chunk, encoding) {
     } else {
       // buffer, or a non-toString-friendly encoding
       len = chunk.length;
-      this._send(len.toString(16) + CRLF);
-      this._send(chunk, encoding);
-      ret = this._send(CRLF);
+
+      if (this.connection)
+        this.connection.cork();
+      this._send(len.toString(16));
+      this._send(crlf_buf);
+      this._send(chunk);
+      ret = this._send(crlf_buf);
+      if (this.connection)
+        this.connection.uncork();
     }
   } else {
     ret = this._send(chunk, encoding);