Molex USB Micro AB Eagle Package
We have had the same issue with similar USB connectors.
At the present Eagle doesn't have an option for creating slotted pads, however there is a workaround described in this Eagle forum.

In a nutshell, create a component in your library that has (as described by Rachael): 


  A PAD on each end of the slot and then draw each of the inner/outer
  layer pad areas with a polygon on each of the 16 routing layers. Then
  also draw the slot as a line on the Milling layer.


It makes creating slots more time consuming, but once it is in your library then it is reusable as much as you like and should manufacture correctly at there PCB factory.