Fix ReactHorizontalScrollView contentOffset

Summary:
Brings the same fix https://www.internalfb.com/diff/D34015853 (be260b9) for ReactScrollView to ReactHorizontalScrollView

When setting ScrollView's contentOffset, if the ScrollView hasn't been laid out yet when ReactHorizontalScrollViewManager.setContentOffset is called, then scroll position is never set properly. This is because the actual scroll offset (0, 0) was being passed into setPendingContentOffsets, instead of the desired scroll offset. Thus, when ReactHorizontalScrollView.onLayout gets called, ReactHorizontalScrollView.scrollTo gets called with (0, 0).

Changelog:
[Android][Fixed] - Fix ReactHorizontalScrollView contentOffset

Reviewed By: bvanderhoof

Differential Revision: D34246489

fbshipit-source-id: d923f7c9f136f7275d64bd658ffd5c2cc049d392

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

@@ -661,8 +661,7 @@ private int getSnapInterval() {
   }
 
   private View getContentView() {
-    View contentView = getChildAt(0);
-    return contentView;
+    return getChildAt(0);
   }
 
   public void setEndFillColor(int color) {
@@ -1191,12 +1190,13 @@ public void scrollTo(int x, int y) {
     }
 
     super.scrollTo(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();
-    ReactScrollViewHelper.updateFabricScrollState(this, actualX, actualY);
-    setPendingContentOffsets(actualX, actualY);
+    ReactScrollViewHelper.updateFabricScrollState(this);
+    setPendingContentOffsets(x, y);
+  }
+
+  private boolean isContentReady() {
+    View child = getContentView();
+    return child != null && child.getWidth() != 0 && child.getHeight() != 0;
   }
 
   /**
@@ -1210,8 +1210,8 @@ private void setPendingContentOffsets(int x, int y) {
     if (DEBUG_MODE) {
       FLog.i(TAG, "setPendingContentOffsets[%d] x %d y %d", getId(), x, y);
     }
-    View child = getContentView();
-    if (child != null && child.getWidth() != 0 && child.getHeight() != 0) {
+
+    if (isContentReady()) {
       pendingContentOffsetX = UNSET_CONTENT_OFFSET;
       pendingContentOffsetY = UNSET_CONTENT_OFFSET;
     } else {

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

@@ -954,10 +954,13 @@ public void reactSmoothScrollTo(int x, int y) {
   }
 
   /**
-   * Calls `updateFabricScrollState` and updates state.
+   * Calls `super.scrollTo` and updates state.
    *
-   * <p>`scrollTo` changes `contentOffset` and we need to keep `contentOffset` in sync between
-   * scroll view and state. Calling ScrollView's `scrollTo` doesn't update state.
+   * <p>`super.scrollTo` changes `contentOffset` and we need to keep `contentOffset` in sync between
+   * scroll view and state.
+   *
+   * <p>Note that while we can override scrollTo, we *cannot* override `smoothScrollTo` because it
+   * is final. See `reactSmoothScrollTo`.
    */
   @Override
   public void scrollTo(int x, int y) {
@@ -967,7 +970,7 @@ public void scrollTo(int x, int y) {
   }
 
   private boolean isContentReady() {
-    View child = getChildAt(0);
+    View child = getContentView();
     return child != null && child.getWidth() != 0 && child.getHeight() != 0;
   }