[React Native] Fix scroll view sticky headers

Summary:
The `ScrollView` component tells the native side the subview indices of the views to make sticky. The problem is that, once layout-only views are collapsed, the indices are no longer reflective of the original views to make stick to the top.

Author: Alex Akers

Libraries/Components/ScrollView/ScrollView.js

@@ -17,6 +17,7 @@ var PointPropType = require('PointPropType');
 var RCTScrollView = require('NativeModules').UIManager.RCTScrollView;
 var RCTScrollViewConsts = RCTScrollView.Constants;
 var React = require('React');
+var ReactChildren = require('ReactChildren');
 var ReactNativeViewAttributes = require('ReactNativeViewAttributes');
 var RCTUIManager = require('NativeModules').UIManager;
 var ScrollResponder = require('ScrollResponder');
@@ -277,13 +278,24 @@ var ScrollView = React.createClass({
       }
     }
 
+    var children = this.props.children;
+    if (this.props.stickyHeaderIndices) {
+      children = ReactChildren.map(children, (child) => {
+        if (child) {
+          return <View collapsible={false}>{child}</View>;
+        } else {
+          return child;
+        }
+      });
+    }
+
     var contentContainer =
       <View
         collapsible={false}
         ref={INNERVIEW}
         style={contentContainerStyle}
         removeClippedSubviews={this.props.removeClippedSubviews}>
-        {this.props.children}
+        {children}
       </View>;
 
     var alwaysBounceHorizontal =