Save buttons props for root screens

src/deprecated/platformSpecificDeprecated.android.js

       if (button.buttonColor) {
         button.color = processColor(button.buttonColor);
       }
+      if (button.component) {
+        const passPropsKey = _.uniqueId('customButtonComponent');
+        PropRegistry.save(passPropsKey, button.passProps);
+        button.passProps = {passPropsKey};
+      }
     });
   }