Remove captured scroll feature check (#9283)

* Remove captured scroll feature check

IE8 was the only browser that did not support captured scroll. We no
longer have that constraint.

* Remove WINDOW_HANDLE const

src/renderers/dom/shared/ReactBrowserEventEmitter.js

@@ -262,19 +262,11 @@ var ReactBrowserEventEmitter = Object.assign({}, ReactEventEmitterMixin, {
             );
           }
         } else if (dependency === 'topScroll') {
-          if (isEventSupported('scroll', true)) {
-            ReactBrowserEventEmitter.ReactEventListener.trapCapturedEvent(
-              'topScroll',
-              'scroll',
-              mountAt,
-            );
-          } else {
-            ReactBrowserEventEmitter.ReactEventListener.trapBubbledEvent(
-              'topScroll',
-              'scroll',
-              ReactBrowserEventEmitter.ReactEventListener.WINDOW_HANDLE,
-            );
-          }
+          ReactBrowserEventEmitter.ReactEventListener.trapCapturedEvent(
+            'topScroll',
+            'scroll',
+            mountAt,
+          );
         } else if (dependency === 'topFocus' || dependency === 'topBlur') {
           if (isEventSupported('focus', true)) {
             ReactBrowserEventEmitter.ReactEventListener.trapCapturedEvent(

src/renderers/dom/shared/ReactEventListener.js

@@ -12,7 +12,6 @@
 'use strict';
 
 var EventListener = require('fbjs/lib/EventListener');
-var ExecutionEnvironment = require('fbjs/lib/ExecutionEnvironment');
 var PooledClass = require('PooledClass');
 var ReactDOMComponentTree = require('ReactDOMComponentTree');
 var ReactGenericBatching = require('ReactGenericBatching');
@@ -111,8 +110,6 @@ var ReactEventListener = {
   _enabled: true,
   _handleTopLevel: null,
 
-  WINDOW_HANDLE: ExecutionEnvironment.canUseDOM ? window : null,
-
   setHandleTopLevel: function(handleTopLevel) {
     ReactEventListener._handleTopLevel = handleTopLevel;
   },