🚨 Error: a.h.onResizeSuccess is not a function. (In 'a.h.onResizeSuccess()', 'a.h.onResizeSuccess' is undefined)

Details
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**Error report:** [link](http://go/ampe/CJKryMiP2rnINg)
**First seen:** Nov 14, 2018
**Frequency:** ~ 4,201/day

Stacktrace
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Error: a.h.onResizeSuccess is not a function. (In 'a.h.onResizeSuccess()', 'a.h.onResizeSuccess' is undefined)

    at extensions/amp-ad/0.1/amp-ad-xorigin-iframe-handler.js:458:12

Notes
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`@powerivq` modified `extensions/amp-ad/0.1/amp-ad-xorigin-iframe-handler.js:458-458` in #30323 (Sep 24, 2020)

**Seen in:**
- 10-13 Nightly-Control (2225+2)
- 10-13 Nightly-Control (2225+3)
- 10-13 Stable (2225+2)
- 10-22 Beta (2244)
- 10-22 Experiment-A (2244)
- 10-22 Experimental (2244)
- +7 more

/cc @ampproject/release-on-duty

Start by inspecting extensions/amp-ad/0.1/amp-ad-xorigin-iframe-handler.js around line 458 and the referenced change in #30323. Trace why onResizeSuccess is undefined in the reported call path, then verify that the production error no longer occurs across the affected AMP release channels.

Written by the indexing model from the issue text.