RN 0.59.8: postMessage result from iOS WebView is double-encoded

The data returned to onMessage WebView callback on iOS is double-percent-encoded.

React Native version: 0.59.8

Steps To Reproduce

1. Inject a JS into WebView that calls e.g. window.postMessage('https://test.com')
2. The onMessage handler will receive double-encoded value:

<WebView onMessage={onMessage} ... />

function onMessage(event) {
   console.log(event.nativeEvent.data);  // "https%253A%252F%252Ftest.com"
}

This was introduced in https://github.com/facebook/react-native/commit/61ca11965046f75e7500e5152c5f2b60df2a2cd5#diff-17ddfccc3e39071c0aa51f82677e6d68 :

Correct method to use instead of stringByReplacingPercentEscapesUsingEncoding is stringByRemovingPercentEncoding.

cc @pvinis

[t-benze]

somehow adding useWebKit={true} fix the issue.

---

seems the issue only affect UIWebView, not WKWebView

[aijason]

Platform.OS === 'ios' ? decodeURIComponent(decodeURIComponent(event.nativeEvent.data)) : event.nativeEvent.data