src/vs/platform/userDataSync/common/abstractSynchronizer.ts/AbstractInitializer/updateLastSyncUserData
class AbstractInitializer:	protected async updateLastSyncUserData(lastSyncRemoteUserData: IRemoteUserData, additionalProps: IStringDictionary<any> = {}): Promise<void> {
		const lastSyncUserData: IUserData = { ref: lastSyncRemoteUserData.ref, content: lastSyncRemoteUserData.syncData ? JSON.stringify(lastSyncRemoteUserData.syncData) : null, ...additionalProps };
		await this.fileService.writeFile(this.lastSyncResource, VSBuffer.fromString(JSON.stringify(lastSyncUserData)));
	}