Crash report: `ReferenceError: Can't find variable: ResizeObserver`

URL

https://app.uniswap.org/#/swap?chain=mainnet

swap state

{
  "INPUT": {
    "currencyId": "ETH"
  },
  "OUTPUT": {
    "currencyId": "USDC"
  },
  "independentField": "INPUT",
  "typedValue": "1",
  "recipient": null
}

Error

ReferenceError: Can't find variable: ResizeObserver

Stacktrace

https://app.uniswap.org/static/js/35.9bf5c262.chunk.js:2:2787822
https://app.uniswap.org/static/js/35.9bf5c262.chunk.js:2:2787544
https://app.uniswap.org/static/js/35.9bf5c262.chunk.js:2:2787657
ju@https://app.uniswap.org/static/js/35.9bf5c262.chunk.js:2:2955477
ju@[native code]
unstable_runWithPriority@https://app.uniswap.org/static/js/35.9bf5c262.chunk.js:2:2974688
Mu@https://app.uniswap.org/static/js/35.9bf5c262.chunk.js:2:2952097
wu@https://app.uniswap.org/static/js/35.9bf5c262.chunk.js:2:2948183
wu@[native code]
https://app.uniswap.org/static/js/35.9bf5c262.chunk.js:2:2897451
unstable_runWithPriority@https://app.uniswap.org/static/js/35.9bf5c262.chunk.js:2:2974688
Yr@https://app.uniswap.org/static/js/35.9bf5c262.chunk.js:2:2897397
Xr@https://app.uniswap.org/static/js/35.9bf5c262.chunk.js:2:2897332
hu@https://app.uniswap.org/static/js/35.9bf5c262.chunk.js:2:2945335
Fi@https://app.uniswap.org/static/js/35.9bf5c262.chunk.js:2:2916985
Fi@[native code]
https://app.uniswap.org/static/js/main.6148716e.chunk.js:1:27343

Device data

{
  "ua": "Mozilla/5.0 (iPhone; CPU iPhone OS 12_5_5 like Mac OS X) AppleWebKit/605.1.15 (KHTML, like Gecko) Mobile/15E148",
  "browser": {
    "name": "WebKit",
    "version": "605.1.15",
    "major": "605"
  },
  "engine": {
    "name": "WebKit",
    "version": "605.1.15"
  },
  "os": {
    "name": "iOS",
    "version": "12.5.5"
  },
  "device": {
    "vendor": "Apple",
    "model": "iPhone",
    "type": "mobile"
  },
  "cpu": {}
}

Start by reproducing the swap URL on the reported iPhone iOS 12.5.5 WebKit environment and compare it with a supported browser. Use the provided ResizeObserver error and bundled stacktrace to locate the responsible source, then verify that the swap page no longer crashes when ResizeObserver is unavailable.