Trying to add a corner at the top left side of my custom List selector any suggestions?

I want a single corner at the top left side of the list selector

here's the code

<selector xmlns:android="http://ift.tt/nIICcg">
<item android:state_window_focused="false" android:drawable="@android:color/transparent" />

<item android:state_focused="true" 
     android:state_enabled="false" 
     android:state_pressed="true" 
     android:drawable="@drawable/list_selector_disabled_holo_dark" />
<item android:state_focused="true"  
    android:state_enabled="false"     
   android:drawable="@drawable/list_selector_disabled_holo_dark" />

<item android:state_focused="true"                      
      android:state_pressed="true" android:drawable="@drawable/selector" />
<item android:state_focused="false"     
      android:state_pressed="true" android:drawable="@drawable/selector" />
<item android:state_focused="true"             
      android:drawable="@drawable/selector" />