Fix RN accessibility links with UIAutomator

Summary:
D34687371 (7b5b114) unfortunately caused a regression with UIAutomator, where it would no longer be able to see any Views that have the ReactAccessibilityDelegate attached to them. This was because the delegate was changed to extend ExploreByTouchHelper which implements its own default AccessibilityNodeProvider, which does nothing in the case of a view without any virtual children.

This diff simply *only* uses the node provider if the view in question has virtual children, otherwise defaulting to the standard behavior from the View class.

Changelog:
[Android][Fixed] - Fixed issue where any node with an AccessibilityDelegate set (which was any node with any accessibility propoerty), was using ExploreByTouchHelper's built in AccessibilityNodeProvider, and not properly populating their AccessibilityNodeInfo's, leading to focus issues and issues with automated test services like UIAutomator.

Reviewed By: kacieb

Differential Revision: D35601320

fbshipit-source-id: 92e009c6e8b4ddcab860e2c91e6bd1a8f95359f0

Author: blavalla

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

@@ -27,6 +27,7 @@
 import androidx.core.view.accessibility.AccessibilityNodeInfoCompat;
 import androidx.core.view.accessibility.AccessibilityNodeInfoCompat.AccessibilityActionCompat;
 import androidx.core.view.accessibility.AccessibilityNodeInfoCompat.RangeInfoCompat;
+import androidx.core.view.accessibility.AccessibilityNodeProviderCompat;
 import androidx.customview.widget.ExploreByTouchHelper;
 import com.facebook.react.R;
 import com.facebook.react.bridge.Arguments;
@@ -684,4 +685,20 @@ private static class AccessibleLink {
       public int id;
     }
   }
+
+  @Override
+  public @Nullable AccessibilityNodeProviderCompat getAccessibilityNodeProvider(View host) {
+    // Only set a NodeProvider if we have virtual views, otherwise just return null here so that
+    // we fall back to the View class's default behavior. If we don't do this, then Views with
+    // no virtual children will fall back to using ExploreByTouchHelper's onPopulateNodeForHost
+    // method to populate their AccessibilityNodeInfo, which defaults to doing nothing, so no
+    // AccessibilityNodeInfo will be created. Alternatively, we could override
+    // onPopulateNodeForHost instead, and have it create an AccessibilityNodeInfo for the host
+    // but this is what the default View class does by itself, so we may as well defer to it.
+    if (mAccessibilityLinks != null) {
+      return super.getAccessibilityNodeProvider(host);
+    }
+
+    return null;
+  }
 }