Fetch Headers constructor should support string[][] parameter

[egorshulga]

Is this a bug report?

Yes

Have you read the Contributing Guidelines?

Yes

Environment

Environment:
OS: Windows 10
Node: 8.9.4
Yarn: 1.3.2
npm: 5.6.0
Watchman: Not Found
Xcode: N/A
Android Studio: Not Found

Packages: (wanted => installed)
react: ^16.2.0 => 16.2.0
react-native: 0.52.0 => 0.52.0

Steps to Reproduce

const headersArray = [
  ['Content-Type', 'application/json'],
  ['Authorization', 'Bearer token']
];
const headers = new Headers(headersArray);
console.log(headers.get('Content-Type'));

Expected Behavior

(In debug console):
application/json

Actual Behavior

(In debug console):
null

The issue occurred when I tried to share working code of fetch calls between a usual React project and a RN project. In React (in chrome) this code works perfectly, but RN cannot initialize Headers using string[][] parameter.

Here is an example of creating Headers from array of arrays.

[egorshulga]

I found that you use whatwg-fetch implementation of fetch.

The PR addressing this issue was merged and released in march 2017 (v2.0.3).
In packages.json: "whatwg-fetch": "^1.0.0".
Could this dependency been updated to the latest version?

I found that the update has been proposed in #12962. Could it be considered now?

[react-native-bot]

Thanks for posting this! It looks like you may not be using the latest version of React Native, v0.53.0, released on January 2018. Can you make sure this issue can still be reproduced in the latest version?

I am going to close this, but please feel free to open a new issue if you are able to confirm that this is still a problem in v0.53.0 or newer.

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