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

URL

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

swap state

{
  "independentField": "INPUT",
  "recipient": null,
  "INPUT": {
    "currencyId": "0xA0b86991c6218b36c1d19D4a2e9Eb0cE3606eB48"
  },
  "OUTPUT": {
    "currencyId": "ETH"
  },
  "typedValue": "5"
}

Error

ReferenceError: Can't find variable: ResizeObserver

Stacktrace

https://app.uniswap.org/static/js/96.eb45b585.chunk.js:2:3345562
https://app.uniswap.org/static/js/96.eb45b585.chunk.js:2:3345284
https://app.uniswap.org/static/js/96.eb45b585.chunk.js:2:3345397
Ru@https://app.uniswap.org/static/js/96.eb45b585.chunk.js:2:3502386
Ru@[native code]
unstable_runWithPriority@https://app.uniswap.org/static/js/96.eb45b585.chunk.js:2:3521597
Du@https://app.uniswap.org/static/js/96.eb45b585.chunk.js:2:3499006
wu@https://app.uniswap.org/static/js/96.eb45b585.chunk.js:2:3495092
wu@[native code]
https://app.uniswap.org/static/js/96.eb45b585.chunk.js:2:3444360
unstable_runWithPriority@https://app.uniswap.org/static/js/96.eb45b585.chunk.js:2:3521597
Zr@https://app.uniswap.org/static/js/96.eb45b585.chunk.js:2:3444306
Kr@https://app.uniswap.org/static/js/96.eb45b585.chunk.js:2:3444241
https://app.uniswap.org/static/js/96.eb45b585.chunk.js:2:3515557
Ie@https://app.uniswap.org/static/js/96.eb45b585.chunk.js:2:3515560
Le@https://app.uniswap.org/static/js/96.eb45b585.chunk.js:2:3414603
https://app.uniswap.org/static/js/96.eb45b585.chunk.js:2:3435794
Cf@https://app.uniswap.org/static/js/96.eb45b585.chunk.js:2:3435798
$t@https://app.uniswap.org/static/js/96.eb45b585.chunk.js:2:3423853
Yt@https://app.uniswap.org/static/js/96.eb45b585.chunk.js:2:3423079
Yt@[native code]
unstable_runWithPriority@https://app.uniswap.org/static/js/96.eb45b585.chunk.js:2:3521597
Re@https://app.uniswap.org/static/js/96.eb45b585.chunk.js:2:3515354
Zt@https://app.uniswap.org/static/js/96.eb45b585.chunk.js:2:3422871
Zt@[native code]

Device data

{
  "ua": "Mozilla/5.0 (iPhone; CPU iPhone OS 12_4_4 like Mac OS X) AppleWebKit/605.1.15 (KHTML, like Gecko) Version/12.1.2 Mobile/15E148 Safari/604.1",
  "browser": {
    "name": "Mobile Safari",
    "version": "12.1.2",
    "major": "12"
  },
  "engine": {
    "name": "WebKit",
    "version": "605.1.15"
  },
  "os": {
    "name": "iOS",
    "version": "12.4.4"
  },
  "device": {
    "vendor": "Apple",
    "model": "iPhone",
    "type": "mobile"
  },
  "cpu": {}
}

Start by reproducing the swap URL on the reported iPhone iOS 12.4.4 Mobile Safari environment and inspect the stack trace for the source of the ResizeObserver reference. Trace that reference to the relevant frontend entry point; done means the swap page no longer crashes in this environment.