src/vs/platform/extensionManagement/node/extensionManagementService.ts/ExtensionManagementService/watchForExtensionsNotInstalledBySystem
class ExtensionManagementService:	private async watchForExtensionsNotInstalledBySystem(): Promise<void> {
		this._register(this.extensionsScanner.onExtract(resource => this.knownDirectories.add(resource)));
		const stat = await this.fileService.resolve(this.extensionsScannerService.userExtensionsLocation);
		for (const childStat of stat.children ?? []) {
			if (childStat.isDirectory) {
				this.knownDirectories.add(childStat.resource);
			}
		}
		this._register(this.fileService.watch(this.extensionsScannerService.userExtensionsLocation));
		this._register(this.fileService.onDidFilesChange(e => this.onDidFilesChange(e)));
	}