Timeline analysis:
- There's a setInterval loop every 10ms throughout the loading process. This happens on all page views because even if not in-sample, there is oversampling and savetiming that run from onLoadCallback.
- Ironically, during an in-sample page view of a simple page with nothing else on it, the only thing that polling loop is waiting for is our own lazy-load for ext.eventLogging and schema.NavigationTiming (the load event waits for all subresources added before the load event, including async scripts).
I propose two changes:
- Get rid of the setInterval loop. This was added because in 2015 we didn't consider a simple check based on timing.loadEventStart, or document.readyState.
- Get rid of the extra EL requests once T187207 settles.