src/vs/platform/userDataSync/common/abstractSynchronizer.ts/AbstractSynchroniser/migrateLastSyncUserData
class AbstractSynchroniser:	private async migrateLastSyncUserData(): Promise<string | undefined> {
		try {
			const content = await this.fileService.readFile(this.lastSyncResource);
			const userData = JSON.parse(content.value.toString());
			await this.fileService.del(this.lastSyncResource);
			if (userData.ref && userData.content !== undefined) {
				this.storageService.store(this.lastSyncUserDataStateKey, JSON.stringify({
					...userData,
					content: undefined,
				}), StorageScope.APPLICATION, StorageTarget.MACHINE);
				await this.writeLastSyncStoredRemoteUserData({ ref: userData.ref, syncData: userData.content === null ? null : JSON.parse(userData.content) });
			}
		} catch (error) {
			if (error instanceof FileOperationError && error.fileOperationResult === FileOperationResult.FILE_NOT_FOUND) {
				this.logService.debug(`${this.syncResourceLogLabel}: Migrating last sync user data. Resource does not exist.`);
			} else {
				this.logService.error(error);
			}
		}
		return this.storageService.get(this.lastSyncUserDataStateKey, StorageScope.APPLICATION);
	}