Summary:This prevents possible developer errors when using 'post' or 'put' instead of 'POST' and 'PUT'.
Fixes: https://github.com/facebook/react-native/issues/6855
**Test plan:**
Previously, a `method put must not have a request body` error would be thrown when the method was in lowercase and a request body was indeed included.
With this fix and the following code (note the method name in all lowercase), the request is properly completed.
```javascript
const url = 'http://myurl.com';
const request = new XMLHttpRequest();
request.open('put', url);
request.setRequestHeader("Content-type","application/json");
request.onload = function() {
console.log('onload');
};
request.onerror = function() {
console.log('error');
};
request.send(JSON.stringify({ something: 'here' }));
```
Closes https://github.com/facebook/react-native/pull/6956
Differential Revision: D3173467
Pulled By: davidaurelio
fb-gh-sync-id: add90e9f31cd4f548547a3f85267a782ae74a89c
fbshipit-source-id: add90e9f31cd4f548547a3f85267a782ae74a89c
4450d789e0