Fix infinite retry loop (#1248)

(Together with a pr to react-native facebook/react-native#22625)
Fixes facebook/react-native#21030

Author: msand

packages/react-devtools-core/src/backend.js

@@ -67,7 +67,7 @@ function connectToDevTools(options: ?ConnectOptions) {
   // See D6251744.
   var ws = websocket ? websocket : new window.WebSocket(uri);
   ws.onclose = handleClose;
-  ws.onerror = handleClose;
+  ws.onerror = handleFailed;
   ws.onmessage = handleMessage;
   ws.onopen = function() {
     var wall = {
@@ -92,6 +92,12 @@ function connectToDevTools(options: ?ConnectOptions) {
       closeListeners.forEach(fn => fn());
     }
   }
+  function handleFailed() {
+    if (!hasClosed) {
+      hasClosed = true;
+      closeListeners.forEach(fn => fn());
+    }
+  }
 
   function handleMessage(evt) {
     var data;