Revert "Don't wrap drag events in IE/Edge in dev builds" (facebook#6741)

src/shared/utils/ReactErrorUtils.js

@@ -11,8 +11,6 @@
 
 'use strict';
 
-var SyntheticDragEvent = require('SyntheticDragEvent');
-
 var caughtError = null;
 
 /**
@@ -67,11 +65,6 @@ if (__DEV__) {
       typeof document.createEvent === 'function') {
     var fakeNode = document.createElement('react');
     ReactErrorUtils.invokeGuardedCallback = function(name, func, a, b) {
-      if (!canWrapEvent(a)) {
-        invokeGuardedCallback(name, func, a, b);
-        return;
-      }
-
       var boundFunc = func.bind(null, a, b);
       var evtType = `react-${name}`;
       fakeNode.addEventListener(evtType, boundFunc, false);
@@ -81,41 +74,6 @@ if (__DEV__) {
       fakeNode.removeEventListener(evtType, boundFunc, false);
     };
   }
-
-  var cacheCanWrapEvent = null;
-
-  /**
-   * IE and Edge don't allow access to the DataTransfer.dropEffect property when
-   * it's wrapped in another event. This function detects whether we're in an
-   * environment that behaves this way.
-   *
-   * @param {*} ev Event that is being tested
-   */
-  function canWrapEvent(ev) {
-    if (!(ev instanceof SyntheticDragEvent)) {
-      return true;
-    } else if (cacheCanWrapEvent !== null) {
-      return cacheCanWrapEvent;
-    }
-
-    var canAccessDropEffect = false;
-    function handleWrappedEvent() {
-      try {
-        ev.dataTransfer.dropEffect; // eslint-disable-line no-unused-expressions
-        canAccessDropEffect = true;
-      } catch (e) {}
-    }
-
-    var wrappedEventName = 'react-wrappeddragevent';
-    var wrappedEvent = document.createEvent('Event');
-    wrappedEvent.initEvent(wrappedEventName, false, false);
-    fakeNode.addEventListener(wrappedEventName, handleWrappedEvent, false);
-    fakeNode.dispatchEvent(wrappedEvent);
-    fakeNode.removeEventListener(wrappedEventName, handleWrappedEvent, false);
-
-    cacheCanWrapEvent = canAccessDropEffect;
-    return canAccessDropEffect;
-  }
 }
 
 module.exports = ReactErrorUtils;