After #13937, platform channels work on background isolates. Plugins should work as well, but if a plugin relies on a dart plugin registrant (example shared_preferences usage to set the platform_interface subclass) the registrant isn't executed on the background isolate, so the plugin doesn't function correctly. Specifically there aren't handlers registered for the platform channels.

The solution should be to execute the Dart plugin registrant on the background isolate when it registers with the root isolate.

See:

• PlatformConfigurationNativeApi::RegisterBackgroundIsolate
• flutter::FindAndInvokeDartPluginRegistrant