Summary:
In `XMLHttpRequest`, if the responseType is `Blob`, but the response is an empty string, we return `null` from `XMLHttpRequest.prototype.response()`. Instead, we should return an empty Blob. This is the behaviour on the web. To demonstrate, run the following HTTP server with Node:
## server.js
```
const http = require('http');
const server = http.createServer();
server.on('request', (request, response) => {
if (request.url.includes('img.png')) {
console.log('sending image');
response.end('');
return;
}
response.end('Hello World!');
});
server.listen('9000');
```
Then, open up a web browser to `http://localhost:9000`, and type the following in the console:
```
var oReq = new XMLHttpRequest();
oReq.open('GET', 'http://localhost:9000/img.png', true);
oReq.responseType = 'blob';
oReq.onload = function(oEvent) {
var blob = oReq.response;
console.warn(blob);
};
oReq.onerror = function(error) {
console.warn('Error!');
};
oReq.send();
```
This warns:
```
Blob {size: 0, type: "text/xml"}
```
Changelog:
[Both][Fixed] - [RN][XMLHttpRequest] Transform empty responses into empty Blobs
Reviewed By: sahrens
Differential Revision: D19500607
fbshipit-source-id: ec35e534b32a507c8a94a29e955b7bc4c62902a0
9a8c06b502
