conditionalVariants property
Maps a browser .template.dart URI to its native/VM .template.dart
counterpart, for files that use a conditional export
(export 'a_browser.dart' if (dart.library.io) 'a_vm.dart').
The browser URI is the one linked unconditionally (and present in urlsNeedingInitReflector); the emitter turns it into a conditional import so the VM resolves the native variant instead.
Implementation
final Map<String, String> conditionalVariants;