Toolbar item in the left in Android

Hi, I am working with modal pages in xamarin forms and I would like to be able to close them using a button in the toolbar located in the left.
I can put buttons in the right with not problem but they doesn't look intuitive for a back button.
I've seen that this was accomplished for ios in here (http://forums.xamarin.com/discussion/comment/67915/#Comment_67915) but my problem is in android.
I attach a picture of how I would like my button to look.
Regards, Bruno.