src/vs/platform/userDataSync/common/abstractSynchronizer.ts/AbstractSynchroniser/resolveContent
class AbstractSynchroniser:	async resolveContent(uri: URI): Promise<string | null> {
		const ref = this.extUri.basename(uri);
		if (this.extUri.isEqual(uri, this.toRemoteBackupResource(ref))) {
			const { content } = await this.getUserData(ref);
			return content;
		}
		if (this.extUri.isEqual(uri, this.toLocalBackupResource(ref))) {
			return this.userDataSyncBackupStoreService.resolveContent(this.resource, ref);
		}
		return null;
	}