Summary: registerMobileLoggingSchemasModule should be refactored to use $resourceLoader->register
The registration hook is to register modules. Don't use it to add entries to $wgResourceModules.
This was never supported and happened to work since the hook was run in ResourceLoader.php exactly one line before the modules from wgResourceModules are registered.
This is changing in MediaWiki 1.26 and therefore this code must too.
Other extensions always used register() when inside the ResourceLoaderRegisterModules hook, that's what the hook is for.
To register modules in $wgResourceModules, either add them statically (in extension.json or the PHP entry point). Or, to add them dynamically, do so from a setup hook (e.g. wgExtensionFunctions).
The main culprit is MobileFrontendHooks::registerMobileLoggingSchemasModule which is re-used in multiple code pieces instead of explicitly doing it from one place.