src/vs/platform/userDataSync/common/abstractSynchronizer.ts/AbstractSynchroniser/updateRemoteUserData
class AbstractSynchroniser:	protected async updateRemoteUserData(content: string, ref: string | null): Promise<IRemoteUserData> {
		const machineId = await this.currentMachineIdPromise;
		const syncData: ISyncData = { version: this.version, machineId, content };
		ref = await this.userDataSyncStoreService.write(this.resource, JSON.stringify(syncData), ref, this.syncHeaders);
		return { ref, syncData };
	}