Flow type and codegen RCTFbMap

Summary:
Flow type for Android-only RCTFbMap component.

ViewManager in Java here: https://our.intern.facebook.com/intern/diffusion/FBS/browse/master/fbandroid/java/com/facebook/catalyst/views/maps/ReactFbMapViewManager.java

View in Java here: https://our.intern.facebook.com/intern/diffusion/FBS/browse/master/fbandroid/java/com/facebook/catalyst/views/maps/ReactFbMapView.java

Reviewed By: TheSavior

Differential Revision: D16811331

fbshipit-source-id: 210d80143b4826fc2ffb3402066c8fd0653e6794

packages/react-native-codegen/src/parsers/flow/components/props.js

@@ -118,7 +118,7 @@ function getTypeAnnotationForArray(name, typeAnnotation, defaultValue, types) {
       };
     default:
       (type: empty);
-      throw new Error(`Unknown prop type for "${name}"`);
+      throw new Error(`Unknown prop type for "${name}": ${type}`);
   }
 }