net: Don't go through Stream API when ondata is used

This speeds up http_simple by around 6%.

lib/net.js

@@ -461,7 +461,10 @@ function onread(buffer, offset, length) {
     // if it's not enough data, we'll just call handle.readStart()
     // again right away.
     self.bytesRead += length;
-    self._readableState.onread(null, buffer.slice(offset, end));
+
+    // Optimization: emit the original buffer with end points
+    if (self.ondata) self.ondata(buffer, offset, end);
+    else self._readableState.onread(null, buffer.slice(offset, end));
 
     if (handle.reading && !self._readableState.reading) {
       handle.reading = false;
@@ -471,9 +474,6 @@ function onread(buffer, offset, length) {
         self._destroy(errnoException(errno, 'read'));
     }
 
-    // Optimization: emit the original buffer with end points
-    if (self.ondata) self.ondata(buffer, offset, end);
-
   } else if (errno == 'EOF') {
     debug('EOF');