[RUM] LinkedIn Insight Tag throws unhandled "window.lintrk is not a function" — our global insertBefore patch puts a first-party frame on every vendor tag's stack

[dawsontoth]

window.lintrk is not a function reaches Error Tracking as an unhandled TypeError:
24 events across 5 sessions in 30 days, 12 of them from a single session in the last 24h. All on
the / entry point.

lintrk appears nowhere in this repo. It is the LinkedIn Insight Tag, injected by the GTM container
(GTM-5QQX432, loaded from useGTM() in src/App.tsx). GTM inserts an inline snippet that calls
window.lintrk(...); when snap.licdn.com/li.lms-analytics/insight.min.js has not loaded — blocked
by an ad blocker, or just slower than the snippet — the call throws.

Why shouldKeepEvent cannot drop it

The stack is:

TypeError: window.lintrk is not a function
  at <anonymous> @ <anonymous>:1:8                          <- GTM's inline script
  at Node.insertBefore @ .../assets/index-D9wn3O9N.js:825:42836   <- OUR code
  at <anonymous> @ https://www.googletagmanager.com/...
  at CS @ https://www.googletagmanager.com/...
  ... (all remaining frames googletagmanager.com)

originatesInThirdPartyScript in src/integrations/datadog/shouldKeepEvent.ts returns false as
soon as one located frame is neither static.reo.dev, nor *-extension://, nor
/assets/vendor-datadog-*.js. The Node.insertBefore frame is ours: it is
src/lib/installBrowserTranslationDomGuard.ts:52-53, which patches Node.prototype.insertBefore
globally (the #1388 browser-translation fix). Confirmed by reading the deployed chunk at exactly that
offset:

let r=Node.prototype.insertBefore;Node.prototype.insertBefore=function(e,t){
  return t instanceof Node&&t.parentNode!==this?r.call(this,e,null):r.call(this,e,t)}

So the filter is working as written — but that global patch puts a first-party frame on the stack of
every third-party script that inserts a DOM node, and an inline <script> executes synchronously
during insertion, so anything it throws propagates through our frame. This is broader than LinkedIn:
any vendor tag that throws while being injected is now attributed to Studio.

Options

• Add www.googletagmanager.com (and snap.licdn.com) to THIRD_PARTY_SCRIPT_FRAME. Smallest change,
  and consistent with the comment already on that constant.
• Or make originatesInThirdPartyScript treat the DOM-guard frame the way it treats
  INSTRUMENTATION_FRAME — it is our code but it is never the cause, only a shim on the path. This
  is the more general fix, and it would also cover the next vendor tag.

Volume is low, so this is hygiene rather than urgent: it costs one Error Tracking issue and a
bursty 12-events-per-session tail. Related third-party-attribution issues: #1645, #1659, #1620.
Related to #1684, which covers the cost of loading these tags eagerly in the first place.