[Tracking Requested - why for this release]:

Version increase simulation:
https://treeherder.mozilla.org/#/jobs?repo=try&resultStatus=testfailed%2Cbusted%2Cexception&classifiedState=unclassified&revision=b8832c913b1c7150d74456e803a49ebe41d376f2&selectedJob=264549506

Log link: https://treeherder.mozilla.org/logviewer.html#/jobs?job_id=264549506&repo=try&lineNumber=1599

Log snippet:
[task 2019-09-02T11:36:26.447Z] 11:36:26 INFO - TEST-INFO | started process screencapture
[task 2019-09-02T11:36:26.598Z] 11:36:26 INFO - TEST-INFO | screencapture: exit 0
[task 2019-09-02T11:36:26.598Z] 11:36:26 INFO - Buffered messages logged at 11:36:16
[task 2019-09-02T11:36:26.598Z] 11:36:26 INFO - Entering test bound checkTelemetryClickEvents
[task 2019-09-02T11:36:26.598Z] 11:36:26 INFO - Loading a bad cert page and verifying telemetry click events arrive.
[task 2019-09-02T11:36:26.598Z] 11:36:26 INFO - Buffered messages logged at 11:36:18
[task 2019-09-02T11:36:26.598Z] 11:36:26 INFO - Loading and waiting for the cert error
[task 2019-09-02T11:36:26.598Z] 11:36:26 INFO - Buffered messages finished
[task 2019-09-02T11:36:26.598Z] 11:36:26 INFO - TEST-UNEXPECTED-FAIL | browser/base/content/test/about/browser_aboutCertError_telemetry.js | Uncaught exception - recorded telemetry for the load - timed out after 50 tries.
[task 2019-09-02T11:36:26.598Z] 11:36:26 INFO - Leaving test bound checkTelemetryClickEvents
[task 2019-09-02T11:36:26.598Z] 11:36:26 INFO - GECKO(1640) | JavaScript error: resource://testing-common/PromiseTestUtils.jsm, line 112: uncaught exception: Object
[task 2019-09-02T11:36:26.598Z] 11:36:26 INFO - Console message: [JavaScript Error: "uncaught exception: Object" {file: "resource://testing-common/PromiseTestUtils.jsm" line: 112}]
[task 2019-09-02T11:36:26.598Z] 11:36:26 INFO - GECKO(1640) | MEMORY STAT | vsize 7647MB | residentFast 324MB | heapAllocated 107MB
[task 2019-09-02T11:36:26.598Z] 11:36:26 INFO - TEST-OK | browser/base/content/test/about/browser_aboutCertError_telemetry.js | took 10032ms
[task 2019-09-02T11:36:26.598Z] 11:36:26 INFO - Not taking screenshot here: see the one that was previously logged
[task 2019-09-02T11:36:26.598Z] 11:36:26 INFO - TEST-UNEXPECTED-FAIL | browser/base/content/test/about/browser_aboutCertError_telemetry.js | Found an unexpected tab at the end of test run: https://expired.example.com/ -
[task 2019-09-02T11:36:26.598Z] 11:36:26 INFO - GECKO(1640) | ++DOCSHELL 0x114944800 == 1 [pid = 1646] [id = {e1946c7b-ac62-d24b-a25f-2c5fe14e4cb2}]
[task 2019-09-02T11:36:26.598Z] 11:36:26 INFO - GECKO(1640) | ++DOMWINDOW == 1 (0x11de3f020) [pid = 1646] [serial = 52] [outer = 0x0]
[task 2019-09-02T11:36:26.598Z] 11:36:26 INFO - GECKO(1640) | ++DOMWINDOW == 2 (0x10f694c00) [pid = 1646] [serial = 53] [outer = 0x11de3f020]
[task 2019-09-02T11:36:26.598Z] 11:36:26 INFO - GECKO(1640) | ++DOMWINDOW == 3 (0x1149e5c00) [pid = 1646] [serial = 54] [outer = 0x11de3f020]
[task 2019-09-02T11:36:26.612Z] 11:36:26 INFO - checking window state

I think we can safely remove the event telemetry from about:certerror now. Prathiksha, I know we talked about this previously, do you have time/interest to take this bug?

Didn't mean to take the bug :)

https://hg.mozilla.org/mozilla-central/rev/273eb2dbb0e3

Verified fixed with latest version increase simulation: https://treeherder.mozilla.org/#/jobs?repo=try&group_state=expanded&resultStatus=testfailed%2Cbusted%2Cexception&revision=b30d003a9e626cc9ace7f954c0a5eebbb2d5c9cd