Scrollview updatedChildFrames data controlled by prop

Summary: Optimize ScrollView by adding flag "DEPRECATED_sendUpdatedChildFrames" to gate whether updatedChildFrames data is computed and propagated on scroll events.  The frame data is used in ListView by the onChangeVisibleRows prop.  When this prop is not defined, unnecessary computation in ScrollView should not be performed.

Reviewed By: sahrens

Differential Revision: D5174898

fbshipit-source-id: e3eaed8760b76becf14dfeb00122bdebdaeae4ef

Libraries/Components/ScrollView/ScrollView.js

@@ -388,6 +388,15 @@ const ScrollView = React.createClass({
       'always',
       'never',
     ]),
+    /**
+     * When true, ScrollView will emit updateChildFrames data in scroll events,
+     * otherwise will not compute or emit child frame data.  This only exists
+     * to support legacy issues, `onLayout` should be used instead to retrieve
+     * frame data.
+     * The default value is false.
+     * @platform ios
+     */
+    DEPRECATED_sendUpdatedChildFrames: PropTypes.bool,
   },
 
   mixins: [ScrollResponder.Mixin],
@@ -682,6 +691,9 @@ const ScrollView = React.createClass({
         this.props.alwaysBounceVertical :
         !this.props.horizontal;
 
+    const DEPRECATED_sendUpdatedChildFrames =
+      !!this.props.DEPRECATED_sendUpdatedChildFrames;
+
     const baseStyle = this.props.horizontal ? styles.baseHorizontal : styles.baseVertical;
     const props = {
       ...this.props,
@@ -710,6 +722,7 @@ const ScrollView = React.createClass({
       scrollEventThrottle: hasStickyHeaders ? 1 : this.props.scrollEventThrottle,
       sendMomentumEvents: (this.props.onMomentumScrollBegin || this.props.onMomentumScrollEnd) ?
         true : false,
+      DEPRECATED_sendUpdatedChildFrames,
     };
 
     const { decelerationRate } = this.props;