From 471b4af2c8a407c897bbd954b040af297efb10b6 Mon Sep 17 00:00:00 2001
From: Andreas Svensson <andreas@syranide.com>
Date: Mon, 29 Sep 2014 16:59:43 +0200
Subject: [PATCH] Disable ViewportMetrics unless MouseEvent lacks support for
 pageX/pageY

---
 src/renderers/dom/client/ReactBrowserEventEmitter.js | 12 ++++++++++--
 1 file changed, 10 insertions(+), 2 deletions(-)

diff --git a/src/renderers/dom/client/ReactBrowserEventEmitter.js b/src/renderers/dom/client/ReactBrowserEventEmitter.js
index 7f203aace9c6c..00cc48902497a 100644
--- a/src/renderers/dom/client/ReactBrowserEventEmitter.js
+++ b/src/renderers/dom/client/ReactBrowserEventEmitter.js
@@ -74,6 +74,7 @@ var isEventSupported = require('isEventSupported');
  *    React Core     .  General Purpose Event Plugin System
  */
 
+var hasEventPageXY;
 var alreadyListeningTo = {};
 var isMonitoringScrollValue = false;
 var reactTopListenersCounter = 0;
@@ -345,12 +346,19 @@ var ReactBrowserEventEmitter = assign({}, ReactEventEmitterMixin, {
    * Listens to window scroll and resize events. We cache scroll values so that
    * application code can access them without triggering reflows.
    *
+   * ViewportMetrics is only used by SyntheticMouse/TouchEvent and only when
+   * pageX/pageY isn't supported (legacy browsers).
+   *
    * NOTE: Scroll events do not bubble.
    *
    * @see http://www.quirksmode.org/dom/events/scroll.html
    */
-  ensureScrollValueMonitoring: function() {
-    if (!isMonitoringScrollValue) {
+  ensureScrollValueMonitoring: function(){
+    if (hasEventPageXY === undefined) {
+      hasEventPageXY =
+        document.createEvent && 'pageX' in document.createEvent('MouseEvent');
+    }
+    if (!hasEventPageXY && !isMonitoringScrollValue) {
       var refresh = ViewportMetrics.refreshScrollValues;
       ReactBrowserEventEmitter.ReactEventListener.monitorScrollValue(refresh);
       isMonitoringScrollValue = true;