src/vs/platform/extensionManagement/common/extensionGalleryService.ts/setTelemetry
function setTelemetry(extension: IGalleryExtension, index: number, querySource?: string): void {
	/* __GDPR__FRAGMENT__
	"GalleryExtensionTelemetryData2" : {
		"index" : { "classification": "SystemMetaData", "purpose": "FeatureInsight", "isMeasurement": true },
		"querySource": { "classification": "SystemMetaData", "purpose": "FeatureInsight" }
	}
	*/
	extension.telemetryData = { index, querySource };
}