- Origin header check shouldn't be case sensitive (#27827)

Summary:
Based on [this](https://stackoverflow.com/a/5259004), header names are not case sensitive.
That means that it's valid to pass a header `Origin` or `origin`.

With the current implementation. on Android only, if you pass `Origin`, it will get overwritten by the default origin.

This made me waste a lot of time debugging a problem while trying to connect to a websockets server that required an `origin` header and my implementation was working fine in iOS but not on Android, so I'm suggest changing the logic a little bit to take that into account.

## Changelog

[Android] [Fixed] - Support for case insensitive "Origin" headers for Websockets
Pull Request resolved: https://github.com/facebook/react-native/pull/27827

Test Plan:
Here's a screenshot of that shows the issue before the fix (`Origin` header set, but getting overridden)

![Screen Shot 2020-01-21 at 11 41 33 AM](https://user-images.githubusercontent.com/1247834/72824606-86302900-3c43-11ea-92c2-3d39881495f0.png)

The fix is not that easy to test since it requires a public websocket server that checks for a custom Origin header, but I think the code changes are very small and clear.

Differential Revision: D19578860

Pulled By: cpojer

fbshipit-source-id: d854e887d1b9e8e54da662b2da2ebe08ce65fdbc

ReactAndroid/src/main/java/com/facebook/react/modules/websocket/WebSocketModule.java

@@ -102,6 +102,8 @@ public final class WebSocketModule extends NativeWebSocketModuleSpec {
       builder.addHeader("Cookie", cookie);
     }
 
+    boolean hasOriginHeader = false;
+
     if (options != null
         && options.hasKey("headers")
         && options.getType("headers").equals(ReadableType.Map)) {
@@ -109,19 +111,20 @@ public final class WebSocketModule extends NativeWebSocketModuleSpec {
       ReadableMap headers = options.getMap("headers");
       ReadableMapKeySetIterator iterator = headers.keySetIterator();
 
-      if (!headers.hasKey("origin")) {
-        builder.addHeader("origin", getDefaultOrigin(url));
-      }
-
       while (iterator.hasNextKey()) {
         String key = iterator.nextKey();
         if (ReadableType.String.equals(headers.getType(key))) {
+          if (key.equalsIgnoreCase("origin")) {
+            hasOriginHeader = true;
+          }
           builder.addHeader(key, headers.getString(key));
         } else {
           FLog.w(ReactConstants.TAG, "Ignoring: requested " + key + ", value not a string");
         }
       }
-    } else {
+    }
+
+    if (!hasOriginHeader) {
       builder.addHeader("origin", getDefaultOrigin(url));
     }