Implement touch intercepting in RCTView

Summary:
public React allows excluding certain elements from touch handling by assigning `PointerEvents` filter to them, such as BOX_NONE - this element will not receive touch but its children will, BOX_ONLY - only this element will receive pointer event and not children, NONE - neither this element nor its children will receive pointer events, and AUTO - pointer events are allowed for both this element and its children.

This diff adds PointerEvents support to flat RCTView. Most of the implementation is copied from ReactViewManager/ReactViewGroup. One small change is made to TouchTargetHelper to ensure that it works correctly with virtual nodes when their parent has PointerEvents set to PointerEvents.BOX_NONE.

Reviewed By: ahmedre

Differential Revision: D2784208

fb-gh-sync-id: 4b831f9b1bfb8014a99d7b33534ae7ff7b4ab498

ReactAndroid/src/main/java/com/facebook/react/uimanager/TouchTargetHelper.java

@@ -173,7 +173,23 @@ public class TouchTargetHelper {
       // This view can't be the target, but its children might
       if (view instanceof ViewGroup) {
         View targetView = findTouchTargetView(eventCoords, (ViewGroup) view);
-        return targetView != view ? targetView : null;
+        if (targetView != view) {
+          return targetView;
+        }
+
+        // PointerEvents.BOX_NONE means that this react element cannot receive pointer events.
+        // However, there might be virtual children that can receive pointer events, in which case
+        // we still want to return this View and dispatch a pointer event to the virtual element.
+        // Note that this currently only applies to Nodes/FlatViewGroup as it's the only class that
+        // is both a ViewGroup and ReactCompoundView (ReactTextView is a ReactCompoundView but not a
+        // ViewGroup).
+        if (view instanceof ReactCompoundView) {
+          int reactTag = ((ReactCompoundView)view).reactTagForTouch(eventCoords[0], eventCoords[1]);
+          if (reactTag != view.getId()) {
+            // make sure we exclude the View itself because of the PointerEvents.BOX_NONE
+            return view;
+          }
+        }
       }
       return null;