Turn on Flow for EventEmitter

Reviewed By: sahrens

Differential Revision: D5732809

fbshipit-source-id: b8241120188b2b64af12249b2f00a43bea3b58a4

Libraries/EventEmitter/MissingNativeEventEmitterShim.js

@@ -38,7 +38,7 @@ class MissingNativeEventEmitterShim extends EventEmitter {
   }
 
   // EventEmitter
-  addListener(eventType: string, listener: Function, context: ?Object): EmitterSubscription {
+  addListener(eventType: string, listener: Function, context: ?Object) {
     this.throwMissingNativeModule();
   }
 

Libraries/Network/XMLHttpRequest.js

@@ -394,7 +394,9 @@ class XMLHttpRequest extends EventTarget(...XHR_EVENTS) {
 
   _clearSubscriptions(): void {
     (this._subscriptions || []).forEach(sub => {
-      sub.remove();
+      if (sub) {
+        sub.remove();
+      }
     });
     this._subscriptions = [];
   }

Libraries/vendor/emitter/EmitterSubscription.js

@@ -7,7 +7,7 @@
  * of patent rights can be found in the PATENTS file in the same directory.
  *
  * @providesModule EmitterSubscription
- * @noflow
+ * @flow
  */
 'use strict';
 

Libraries/vendor/emitter/mixInEventEmitter.js

@@ -18,6 +18,8 @@ const EventHolder = require('EventHolder');
 const invariant = require('fbjs/lib/invariant');
 const keyOf = require('fbjs/lib/keyOf');
 
+import type EmitterSubscription from 'EmitterSubscription';
+
 const TYPES_KEY = keyOf({__types: true});
 
 /**
@@ -79,7 +81,7 @@ const EventEmitterMixin = {
     return this.__getEventEmitter().emitAndHold(eventType, a, b, c, d, e, _);
   },
 
-  addListener: function(eventType, listener, context) {
+  addListener: function(eventType, listener, context): EmitterSubscription {
     return this.__getEventEmitter().addListener(eventType, listener, context);
   },
 

local-cli/templates/HelloNavigation/components/KeyboardSpacer.js

@@ -67,8 +67,8 @@ class KeyboardSpacerIOS extends Component<Props, State> {
     this._unRegisterEvents();
   }
 
-  _keyboardWillShowSubscription: { remove: Function };
-  _keyboardWillHideSubscription: { remove: Function };
+  _keyboardWillShowSubscription: { +remove: Function };
+  _keyboardWillHideSubscription: { +remove: Function };
 
   _registerEvents = () => {
     this._keyboardWillShowSubscription = Keyboard.addListener(