Remove an extra allocation for open source bundles (#11797)

* Remove EventListener fbjs utility

EventListener normalizes event subscription for <= IE8. This is no
longer necessary. element.addEventListener is sufficient.

* Remove an extra allocation for open source bundles

* Split into two functions to avoid extra runtime checks

* Revert unrelated changes

packages/react-dom/src/events/EventListener.js

@@ -0,0 +1,24 @@
+/**
+ * Copyright (c) 2013-present, Facebook, Inc.
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ *
+ * @flow
+ */
+
+export function addEventBubbleListener(
+  element: Element,
+  eventType: string,
+  listener: Function,
+): void {
+  element.addEventListener(eventType, listener, false);
+}
+
+export function addEventCaptureListener(
+  element: Element,
+  eventType: string,
+  listener: Function,
+): void {
+  element.addEventListener(eventType, listener, true);
+}

packages/react-dom/src/events/ReactDOMEventListener.js

@@ -8,8 +8,8 @@
 import {batchedUpdates} from 'events/ReactGenericBatching';
 import {isFiberMounted} from 'react-reconciler/reflection';
 import {HostRoot} from 'shared/ReactTypeOfWork';
-import EventListener from 'fbjs/lib/EventListener';
 
+import {addEventBubbleListener, addEventCaptureListener} from './EventListener';
 import getEventTarget from './getEventTarget';
 import {getClosestInstanceFromNode} from '../client/ReactDOMComponentTree';
 
@@ -124,7 +124,7 @@ export function trapBubbledEvent(topLevelType, handlerBaseName, element) {
   if (!element) {
     return null;
   }
-  return EventListener.listen(
+  addEventBubbleListener(
     element,
     handlerBaseName,
     dispatchEvent.bind(null, topLevelType),
@@ -145,7 +145,7 @@ export function trapCapturedEvent(topLevelType, handlerBaseName, element) {
   if (!element) {
     return null;
   }
-  return EventListener.capture(
+  addEventCaptureListener(
     element,
     handlerBaseName,
     dispatchEvent.bind(null, topLevelType),

packages/react-dom/src/events/forks/EventListener-www.js

@@ -0,0 +1,35 @@
+/**
+ * Copyright (c) 2013-present, Facebook, Inc.
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ *
+ * @flow
+ */
+
+var EventListenerWWW = require('EventListener');
+
+import typeof * as EventListenerType from '../EventListener';
+import typeof * as EventListenerShimType from './EventListener-www';
+
+export function addEventBubbleListener(
+  element: Element,
+  eventType: string,
+  listener: Function,
+): void {
+  EventListenerWWW.listen(element, eventType, listener);
+}
+
+export function addEventCaptureListener(
+  element: Element,
+  eventType: string,
+  listener: Function,
+): void {
+  EventListenerWWW.capture(element, eventType, listener);
+}
+
+// Flow magic to verify the exports of this file match the original version.
+// eslint-disable-next-line no-unused-vars
+type Check<_X, Y: _X, X: Y = _X> = null;
+// eslint-disable-next-line no-unused-expressions
+(null: Check<EventListenerShimType, EventListenerType>);

scripts/flow/environment.js

@@ -24,3 +24,11 @@ declare module 'ReactFiberErrorDialog' {
     showErrorDialog: (error: mixed) => boolean,
   };
 }
+
+// EventListener www fork
+declare module 'EventListener' {
+  declare module.exports: {
+    listen: (target: Element, type: string, callback: Function) => mixed,
+    capture: (target: Element, type: string, callback: Function) => mixed,
+  };
+}

scripts/rollup/forks.js

@@ -101,6 +101,18 @@ const forks = Object.freeze({
         return null;
     }
   },
+
+  // We wrap top-level listeners into guards on www.
+  'react-dom/src/events/EventListener': (bundleType, entry) => {
+    switch (bundleType) {
+      case FB_DEV:
+      case FB_PROD:
+        // Use the www fork which is integrated with TimeSlice profiling.
+        return 'react-dom/src/events/forks/EventListener-www.js';
+      default:
+        return null;
+    }
+  },
 });
 
 module.exports = forks;