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

URL

https://app.uniswap.org/?utm_source=coingecko&utm_content=coingecko&utm_campaign=coingecko&utm_medium=coingecko&utm_term=coingecko#/swap?chain=mainnet

swap state

{
  "independentField": "INPUT",
  "recipient": null,
  "INPUT": {
    "currencyId": "0x426CA1eA2406c07d75Db9585F22781c096e3d0E0"
  },
  "typedValue": "32000",
  "OUTPUT": {
    "currencyId": "ETH"
  }
}

Error

ReferenceError: Can't find variable: ResizeObserver

Stacktrace

https://app.uniswap.org/static/js/3.43095e8b.chunk.js:2:2900039
https://app.uniswap.org/static/js/3.43095e8b.chunk.js:2:2899761
https://app.uniswap.org/static/js/3.43095e8b.chunk.js:2:2899874
ju@https://app.uniswap.org/static/js/3.43095e8b.chunk.js:2:3077181
ju@[native code]
unstable_runWithPriority@https://app.uniswap.org/static/js/3.43095e8b.chunk.js:2:3096392
Du@https://app.uniswap.org/static/js/3.43095e8b.chunk.js:2:3073801
wu@https://app.uniswap.org/static/js/3.43095e8b.chunk.js:2:3069887
wu@[native code]
https://app.uniswap.org/static/js/3.43095e8b.chunk.js:2:3019155
unstable_runWithPriority@https://app.uniswap.org/static/js/3.43095e8b.chunk.js:2:3096392
Yr@https://app.uniswap.org/static/js/3.43095e8b.chunk.js:2:3019101
Xr@https://app.uniswap.org/static/js/3.43095e8b.chunk.js:2:3019036
hu@https://app.uniswap.org/static/js/3.43095e8b.chunk.js:2:3067039
Fi@https://app.uniswap.org/static/js/3.43095e8b.chunk.js:2:3038689
Fi@[native code]
https://app.uniswap.org/static/js/main.cedb5ca8.chunk.js:1:27272

Device data

{
  "ua": "Mozilla/5.0 (iPhone; CPU iPhone OS 12_5_5 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": "12.5.5"
  },
  "device": {
    "vendor": "Apple",
    "model": "iPhone",
    "type": "mobile"
  },
  "cpu": {}
}

Reproduce the swap URL on Mobile Safari 12.1.2 on iOS 12.5.5 and inspect the bundled stack trace. Search the TypeScript frontend source for ResizeObserver usage, then verify that the swap page no longer raises this ReferenceError on the reported environment.