SyncScheduler::ScheduleConfiguration receives a ConfigurationParams argument which (among other things) contains two callbacks, a |ready_task| and a |retry_task|. If CanRunJobNow() is false at the time when the configuration is actually attempted (SyncSchedulerImpl::DoConfigurationSyncCycleJob), then the |retry_task| is run.

The |retry_task| eventually resolves to DataTypeManagerImpl::OnDownloadRetry, where it does... nothing!
The path is: DataTypeManagerImpl::StartNextDownload -> SyncBackendHostImpl::ConfigureDataTypes (inherited via SyncEngine->ModelTypeConfigurer) -> SyncBackendHostCore::DoConfigureSyncer -> SyncManagerImpl::ConfigureSyncer -> SyncSchedulerImpl::ScheduleConfiguration.

Since the whole thing eventually does nothing, let's get rid of all the useless wiring.

Note: SyncSchedulerImpl does keep the |pending_configuration_params_| around in the "retry", so *maybe* the configuration does actually get retried somehow? It's certainly not obvious, and it doesn't require all the wiring back to DataTypeManager.