Fix issue with scrollTo method in ScrollViews to set actual scroll position

Summary:
The `scrollTo` method in ScrollViews are using the `(x, y)` position they got from upperstream to scroll, and to set the state for Fabric. This diff fixes an edge case where the scroll result is not ended up to `(x, y)`. For example, if we are going to scroll to the last item in the list, the item may not scroll to the `(x, y)` position, but stay at the end position of the view.

- Change `scrollTo` method to use the actual `scrollX` and `scrollY` position after scrolling to set current state.

Changelog:
[Android][Fixed] - scrollTo API in ScrollView will check the actual scroll position before setting the scroll state

Reviewed By: JoshuaGross

Differential Revision: D31492685

fbshipit-source-id: e5513fb735ea68c5014b5c47fadffe461cad5c94

Author: ryancat

ReactAndroid/src/main/java/com/facebook/react/views/scroll/ReactHorizontalScrollView.java

@@ -1231,8 +1231,12 @@ public void scrollTo(int x, int y) {
     }
 
     super.scrollTo(x, y);
-    updateStateOnScroll(x, y);
-    setPendingContentOffsets(x, y);
+    // The final scroll position might be different from (x, y). For example, we may need to scroll
+    // to the last item in the list, but that item cannot be move to the start position of the view.
+    final int actualX = getScrollX();
+    final int actualY = getScrollY();
+    updateStateOnScroll(actualX, actualY);
+    setPendingContentOffsets(actualX, actualY);
   }
 
   /**

ReactAndroid/src/main/java/com/facebook/react/views/scroll/ReactScrollView.java

@@ -1006,8 +1006,12 @@ public void onAnimationRepeat(Animator animator) {}
   @Override
   public void scrollTo(int x, int y) {
     super.scrollTo(x, y);
-    updateStateOnScroll(x, y);
-    setPendingContentOffsets(x, y);
+    // The final scroll position might be different from (x, y). For example, we may need to scroll
+    // to the last item in the list, but that item cannot be move to the start position of the view.
+    final int actualX = getScrollX();
+    final int actualY = getScrollY();
+    updateStateOnScroll(actualX, actualY);
+    setPendingContentOffsets(actualX, actualY);
   }
 
   /**