Fixes facebook#3060

Summary: This pull request fixes a glitch that occurred when scrolling horizontally, as described in the facebook#3060.
Closes facebook#3169

Reviewed By: @​svcscm

Differential Revision: D2500186

Pulled By: @mkonicek

Examples/UIExplorer/ScrollViewExample.js

@@ -33,9 +33,9 @@ exports.examples = [
   render: function() {
     return (
       <ScrollView
+        automaticallyAdjustContentInsets={false}
         onScroll={() => { console.log('onScroll!'); }}
         scrollEventThrottle={200}
-        contentInset={{top: -50}}
         style={styles.scrollView}>
         {THUMBS.map(createThumbRow)}
       </ScrollView>
@@ -47,8 +47,8 @@ exports.examples = [
   render: function() {
     return (
       <ScrollView
+        automaticallyAdjustContentInsets={false}
         horizontal={true}
-        contentInset={{top: -50}}
         style={[styles.scrollView, styles.horizontalScrollView]}>
         {THUMBS.map(createThumbRow)}
       </ScrollView>