src/vs/workbench/services/extensionManagement/browser/builtinExtensionsScannerService.ts/BuiltinExtensionsScannerService/constructor
class BuiltinExtensionsScannerService:	constructor(
		@IWorkbenchEnvironmentService environmentService: IWorkbenchEnvironmentService,
		@IUriIdentityService uriIdentityService: IUriIdentityService,
	) {
		if (isWeb) {
			const builtinExtensionsServiceUrl = this._getBuiltinExtensionsUrl(environmentService);
			if (builtinExtensionsServiceUrl) {
				let bundledExtensions: IBundledExtension[] = [];

				if (environmentService.isBuilt) {
					// Built time configuration (do NOT modify)
					bundledExtensions = [/*BUILD->INSERT_BUILTIN_EXTENSIONS*/];
				} else {
					// Find builtin extensions by checking for DOM
					const builtinExtensionsElement = document.getElementById('vscode-workbench-builtin-extensions');
					const builtinExtensionsElementAttribute = builtinExtensionsElement ? builtinExtensionsElement.getAttribute('data-settings') : undefined;
					if (builtinExtensionsElementAttribute) {
						try {
							bundledExtensions = JSON.parse(builtinExtensionsElementAttribute);
						} catch (error) { /* ignore error*/ }
					}
				}

				this.builtinExtensions = bundledExtensions.map(e => ({
					identifier: { id: getGalleryExtensionId(e.packageJSON.publisher, e.packageJSON.name) },
					location: uriIdentityService.extUri.joinPath(builtinExtensionsServiceUrl!, e.extensionPath),
					type: ExtensionType.System,
					isBuiltin: true,
					manifest: e.packageNLS ? localizeManifest(e.packageJSON, e.packageNLS) : e.packageJSON,
					readmeUrl: e.readmePath ? uriIdentityService.extUri.joinPath(builtinExtensionsServiceUrl!, e.readmePath) : undefined,
					changelogUrl: e.changelogPath ? uriIdentityService.extUri.joinPath(builtinExtensionsServiceUrl!, e.changelogPath) : undefined,
				}));
			}
		}
	}