src/vs/platform/userDataSync/common/userDataSyncService.ts/UserDataSyncService/hasPreviouslySynced
class UserDataSyncService:	async hasPreviouslySynced(): Promise<boolean> {
		const result = await this.performSynchronizerAction(async synchronizer => {
			if (await synchronizer.hasPreviouslySynced()) {
				return true;
			}
			return undefined;
		});
		return !!result;
	}