Adding missing @MirrorsUsed targets

A couple of types were missing for @MirrorsUsed when compiling with dart2js and using the dynamic app.

This addresses the question at:
https://groups.google.com/forum/#!topic/angular-dart/DMJZ8fX9oqA

Note that this only appears in the examples if the @MirrorsSyntax is being used:
@MirrorsUsed(
    targets: const [ 'Item' ],
    override: '*')
import 'dart:mirrors';

This impacts people using the previous syntax who have not (or are not) migrated to transformers.