make protocols argument work fixes #5810 fix #6137

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**motivation**

WebSocket spec supports [Sec-WebSocket-Protocol](https://tools.ietf.org/html/rfc6455#section-11.3.4) as a standard way for negotiate a sub protocol between client and server.

* ios WebSocket implementation supports it.
* android WebSocket implementation ignores this header, leave a comment syas: "OkHttp will overrides it", so it did not implement.
* after some test, OkHttp doesn't override the header we add.

**Test plan (required)**

1. run and react-native app on android
2. at the main page, invoke: `var ws = new WebSocket('ws://example.ws-service.fakedomain.com', 'my-sub-protocol');`
3. see the header if it send the correct header, ex, use ngrep: `sudo ngrep -t -Wbyline -deth0 host example.ws-service.fakedomain.com and port 80`

you should see the WebSocket initial GET handshake includes header:
`Sec-WebSocke
Closes #6223

Differential Revision: D3162822

fb-gh-sync-id: a00f1c0f3e1c24ad6aa234329cbb2abad7664264
fbshipit-source-id: a00f1c0f3e1c24ad6aa234329cbb2abad7664264

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

@@ -66,7 +66,6 @@ public String getName() {
 
   @ReactMethod
   public void connect(final String url, @Nullable final ReadableArray protocols, @Nullable final ReadableMap headers, final int id) {
-    // ignoring protocols, since OKHttp overrides them.
     OkHttpClient client = new OkHttpClient();
 
     client.setConnectTimeout(10, TimeUnit.SECONDS);
@@ -99,6 +98,21 @@ public void connect(final String url, @Nullable final ReadableArray protocols, @
       builder.addHeader("origin", setDefaultOrigin(url));
     }
 
+    if (protocols != null && protocols.size() > 0) {
+      StringBuilder protocolsValue = new StringBuilder("");
+      for (int i = 0; i < protocols.size(); i++) {
+        String v = protocols.getString(i).trim();
+        if (!v.isEmpty() && !v.contains(",")) {
+          protocolsValue.append(v);
+          protocolsValue.append(",");
+        }
+      }
+      if (protocolsValue.length() > 0) {
+        protocolsValue.replace(protocolsValue.length() - 1, protocolsValue.length(), "");
+        builder.addHeader("Sec-WebSocket-Protocol", protocolsValue.toString());
+      }
+    }
+
     WebSocketCall.create(client, builder.build()).enqueue(new WebSocketListener() {
 
       @Override