Remove ResizeObserver ponyfill - #31669
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We added this about 6 years ago for Firefox 68 ESR support. According to [CanIUse](https://caniuse.com/?search=ResizeObserver), `ResizeObserver` is well supported now on 95.84% of browsers by usage, and all browsers by _released version_ since early 2020. For Firefox specifically, support was added in 69, and 68 ESR stopped being supported after 78 ESR was released in mid 2020.
tacaswell
approved these changes
May 13, 2026
ksunden
approved these changes
May 15, 2026
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PR summary
We added this about 6 years ago for Firefox 68 ESR support. According to CanIUse,
ResizeObserveris well supported now on 95.84% of browsers by usage, and all browsers by released version since early 2020. For Firefox specifically, support was added in 69, and 68 ESR stopped being supported after 78 ESR was released in mid 2020.AI Disclosure
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