src/vs/platform/extensionManagement/node/extensionsScanner.ts/ExtensionsScanner/setInstalled
class ExtensionsScanner:	async setInstalled(identifierWithVersion: ExtensionIdentifierWithVersion): Promise<ILocalExtension | null> {
		await this.withUninstalledExtensions(uninstalled => delete uninstalled[identifierWithVersion.key()]);
		const installed = await this.scanExtensions(ExtensionType.User);
		const localExtension = installed.find(i => new ExtensionIdentifierWithVersion(i.identifier, i.manifest.version).equals(identifierWithVersion)) || null;
		if (!localExtension) {
			return null;
		}
		await this.storeMetadata(localExtension, { installedTimestamp: Date.now() });
		return this.scanExtension(localExtension.location, ExtensionType.User);
	}